flatbuffers/docs/source/Tutorial.md

Tutorial

Overview

This tutorial provides a basic example of how to work with [FlatBuffers](@ref flatbuffers_overview). We will step through a simple example application, which shows you how to:

• Write a FlatBuffer schema file.
• Use the flatc FlatBuffer compiler.
• Parse JSON files that conform to a schema into FlatBuffer binary files.
• Use the generated files in many of the supported languages (such as C++, Java, and more.)

During this example, imagine that you are creating a game where the main character, the hero of the story, needs to slay some orcs. We will walk through each step necessary to create this monster type using FlatBuffers.

Please select your desired language for our quest: \htmlonly

C++ Java Kotlin C# Go Python JavaScript TypeScript PHP C Dart Lua Lobster Rust Swift \endhtmlonly

\htmlonly

\endhtmlonly

Where to Find the Example Code

Samples demonstating the concepts in this example are located in the source code package, under the samples directory. You can browse the samples on GitHub here.

*Note: The above does not apply to C, instead [look here](https://github.com/dvidelabs/flatcc/tree/master/samples).*

For your chosen language, please cross-reference with:

[sample_binary.cpp](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.cpp)

[SampleBinary.java](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.java)

[SampleBinary.kt](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.kt)

[SampleBinary.cs](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.cs)

[sample_binary.go](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.go)

[sample_binary.py](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.py)

No sample binary is provided, since JS needs to be transpiled from TypeScript. Please see TypeScript support.

none yet

[SampleBinary.php](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.php)

[monster.c](https://github.com/dvidelabs/flatcc/blob/master/samples/monster/monster.c)

[example.dart](https://github.com/google/flatbuffers/blob/master/dart/example/example.dart)

[sample_binary.lua](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.lua)

[sample_binary.lobster](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.lobster)

[sample_binary.rs](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.rs)

[sample_binary.swift](https://github.com/google/flatbuffers/blob/master/samples/sample_binary.swift)

Writing the Monsters' FlatBuffer Schema

To start working with FlatBuffers, you first need to create a schema file, which defines the format for each data structure you wish to serialize. Here is the schema that defines the template for our monsters:

  // Example IDL file for our monster's schema.

  namespace MyGame.Sample;

  enum Color:byte { Red = 0, Green, Blue = 2 }

  union Equipment { Weapon } // Optionally add more tables.

  struct Vec3 {
    x:float;
    y:float;
    z:float;
  }

  table Monster {
    pos:Vec3; // Struct.
    mana:short = 150;
    hp:short = 100;
    name:string;
    friendly:bool = false (deprecated);
    inventory:[ubyte];  // Vector of scalars.
    color:Color = Blue; // Enum.
    weapons:[Weapon];   // Vector of tables.
    equipped:Equipment; // Union.
    path:[Vec3];        // Vector of structs.
  }

  table Weapon {
    name:string;
    damage:short;
  }

  root_type Monster;

As you can see, the syntax for the schema Interface Definition Language (IDL) is similar to those of the C family of languages, and other IDL languages. Let's examine each part of this schema to determine what it does.

The schema starts with a namespace declaration. This determines the corresponding package/namespace for the generated code. In our example, we have the Sample namespace inside of the MyGame namespace.

Next, we have an enum definition. In this example, we have an enum of type byte, named Color. We have three values in this enum: Red, Green, and Blue. We specify Red = 0 and Blue = 2, but we do not specify an explicit value for Green. Since the behavior of an enum is to increment if unspecified, Green will receive the implicit value of 1.

Following the enum is a union. The union in this example is not very useful, as it only contains the one table (named Weapon). If we had created multiple tables that we would want the union to be able to reference, we could add more elements to the union Equipment.

After the union comes a struct Vec3, which represents a floating point vector with 3 dimensions. We use a struct here, over a table, because structs are ideal for data structures that will not change, since they use less memory and have faster lookup.

The Monster table is the main object in our FlatBuffer. This will be used as the template to store our orc monster. We specify some default values for fields, such as mana:short = 150. If unspecified, scalar fields (like int, uint, or float) will be given a default of 0 while strings and tables will be given a default of null. Another thing to note is the line friendly:bool = false (deprecated);. Since you cannot delete fields from a table (to support backwards compatability), you can set fields as deprecated, which will prevent the generation of accessors for this field in the generated code. Be careful when using deprecated, however, as it may break legacy code that used this accessor.

The Weapon table is a sub-table used within our FlatBuffer. It is used twice: once within the Monster table and once within the Equipment union. For our Monster, it is used to populate a vector of tables via the weapons field within our Monster. It is also the only table referenced by the Equipment union.

The last part of the schema is the root_type. The root type declares what will be the root table for the serialized data. In our case, the root type is our Monster table.

The scalar types can also use alias type names such as int16 instead of short and float32 instead of float. Thus we could also write the Weapon table as:

  table Weapon {
    name:string;
    damage:int16;
  }

More Information About Schemas

You can find a complete guide to writing schema files in the [Writing a schema](@ref flatbuffers_guide_writing_schema) section of the Programmer's Guide. You can also view the formal [Grammar of the schema language](@ref flatbuffers_grammar).

Compiling the Monsters' Schema

After you have written the FlatBuffers schema, the next step is to compile it.

If you have not already done so, please follow [these instructions](@ref flatbuffers_guide_building) to build flatc, the FlatBuffer compiler.

Once flatc is built successfully, compile the schema for your language:

*Note: If you're working in C, you need to use the separate project [FlatCC](https://github.com/dvidelabs/flatcc) which contains a schema compiler and runtime library in C for C.*
See [flatcc build instructions](https://github.com/dvidelabs/flatcc#building).
Please be aware of the difference between `flatc` and `flatcc` tools.

~~~{.sh} cd flatbuffers/samples ./../flatc --cpp monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --java monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --kotlin monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --csharp monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --go monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --python monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --ts monster.fbs # customize your TS -> JS transpilation tsc monster_generated.ts ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --ts monster.fbs ~~~

~~~{.sh} cd flatbuffers/sample ./../flatc --php monster.fbs ~~~

~~~{.sh} cd flatcc mkdir -p build/tmp/samples/monster bin/flatcc -a -o build/tmp/samples/monster samples/monster/monster.fbs # or just flatcc/samples/monster/build.sh ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --dart monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --lua monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --lobster monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --rust monster.fbs ~~~

~~~{.sh} cd flatbuffers/samples ./../flatc --swift monster.fbs ~~~

For a more complete guide to using the flatc compiler, please read the [Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) section of the Programmer's Guide.

Reading and Writing Monster FlatBuffers

Now that we have compiled the schema for our programming language, we can start creating some monsters and serializing/deserializing them from FlatBuffers.

Creating and Writing Orc FlatBuffers

The first step is to import/include the library, generated files, etc.

~~~{.cpp} #include "monster_generated.h" // This was generated by `flatc`.

using namespace MyGame::Sample; // Specified in the schema.

</div>
<div class="language-java">
~~~{.java}
  import MyGame.Sample.*; //The `flatc` generated files. (Monster, Vec3, etc.)

  import com.google.flatbuffers.FlatBufferBuilder;

~~~{.kotlin} import MyGame.Sample.* //The `flatc` generated files. (Monster, Vec3, etc.)

import com.google.flatbuffers.FlatBufferBuilder

</div>
<div class="language-csharp">
~~~{.cs}
  using FlatBuffers;
  using MyGame.Sample; // The `flatc` generated files. (Monster, Vec3, etc.)

~~~{.go} import ( flatbuffers "github.com/google/flatbuffers/go" sample "MyGame/Sample" ) ~~~

~~~{.py} import flatbuffers

Generated by flatc.

import MyGame.Sample.Color import MyGame.Sample.Equipment import MyGame.Sample.Monster import MyGame.Sample.Vec3 import MyGame.Sample.Weapon

</div>
<div class="language-javascript">
~~~{.js}
  // The following code is an example - use your desired module flavor by transpiling from TS. 
  var flatbuffers = require('/js/flatbuffers').flatbuffers;
  var MyGame = require('./monster_generated').MyGame; // Generated by `flatc`.

  //--------------------------------------------------------------------------//

  // The following code is for browser-based HTML/JavaScript. Use the above code
  // for JavaScript module loaders (e.g. Node.js).
  <script src="../js/flatbuffers.js"></script>
  <script src="monster_generated.js"></script> // Generated by `flatc`.

~~~{.ts} // note: import flatbuffers with your desired import method

import { MyGame } from './monster_generated';

</div>
<div class="language-php">
~~~{.php}
  // It is recommended that your use PSR autoload when using FlatBuffers in PHP.
  // Here is an example from `SampleBinary.php`:
  function __autoload($class_name) {
    // The last segment of the class name matches the file name.
    $class = substr($class_name, strrpos($class_name, "\\") + 1);
    $root_dir = join(DIRECTORY_SEPARATOR, array(dirname(dirname(__FILE__)))); // `flatbuffers` root.

    // Contains the `*.php` files for the FlatBuffers library and the `flatc` generated files.
    $paths = array(join(DIRECTORY_SEPARATOR, array($root_dir, "php")),
                   join(DIRECTORY_SEPARATOR, array($root_dir, "samples", "MyGame", "Sample")));
    foreach ($paths as $path) {
      $file = join(DIRECTORY_SEPARATOR, array($path, $class . ".php"));
      if (file_exists($file)) {
        require($file);
        break;
      }
    }
  }

~~~{.c} #include "monster_builder.h" // Generated by `flatcc`.

// Convenient namespace macro to manage long namespace prefix. #undef ns #define ns(x) FLATBUFFERS_WRAP_NAMESPACE(MyGame_Sample, x) // Specified in the schema.

// A helper to simplify creating vectors from C-arrays. #define c_vec_len(V) (sizeof(V)/sizeof((V)[0]))

</div>
<div class="language-dart">
~~~{.dart}
  import 'package:flat_buffers/flat_buffers.dart' as fb;

  // Generated by `flatc`.
  import 'monster_my_game.sample_generated.dart' as myGame;

~~~{.lua} -- require the flatbuffers module local flatbuffers = require("flatbuffers")

-- require the generated files from flatc. local color = require("MyGame.Sample.Color") local equipment = require("MyGame.Sample.Equipment") local monster = require("MyGame.Sample.Monster") local vec3 = require("MyGame.Sample.Vec3") local weapon = require("MyGame.Sample.Weapon")

</div>
<div class="language-lobster">
~~~{.lobster}
  import from "../lobster/"  // Where to find flatbuffers.lobster
  import monster_generated

~~~{.rs} // import the flatbuffers runtime library extern crate flatbuffers;

// import the generated code #[allow(dead_code, unused_imports)] #[path = "./monster_generated.rs"] mod monster_generated; pub use monster_generated::my_game::sample::{get_root_as_monster, Color, Equipment, Monster, MonsterArgs, Vec3, Weapon, WeaponArgs};

</div>
<div class="language-swift">
~~~{.swift}
  /**
  // make sure that monster_generated.swift is included in your project
  */
  import Flatbuffers

  // typealiases for convenience
  typealias Monster = MyGame1_Sample_Monster
  typealias Weapon = MyGame1_Sample_Weapon
  typealias Color = MyGame1_Sample_Color
  typealias Vec3 = MyGame1_Sample_Vec3

Now we are ready to start building some buffers. In order to start, we need to create an instance of the FlatBufferBuilder, which will contain the buffer as it grows. You can pass an initial size of the buffer (here 1024 bytes), which will grow automatically if needed:

~~~{.cpp} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. flatbuffers::FlatBufferBuilder builder(1024); ~~~

~~~{.java} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. FlatBufferBuilder builder = new FlatBufferBuilder(1024); ~~~

~~~{.kt} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. val builder = FlatBufferBuilder(1024) ~~~

~~~{.cs} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. var builder = new FlatBufferBuilder(1024); ~~~

~~~{.go} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. builder := flatbuffers.NewBuilder(1024) ~~~

~~~{.py} # Create a `FlatBufferBuilder`, which will be used to create our # monsters' FlatBuffers. builder = flatbuffers.Builder(1024) ~~~

~~~{.js} // Create a `flatbuffer.Builder`, which will be used to create our // monsters' FlatBuffers. var builder = new flatbuffers.Builder(1024); ~~~

~~~{.ts} // Create a `flatbuffer.Builder`, which will be used to create our // monsters' FlatBuffers. let builder = new flatbuffers.Builder(1024); ~~~

~~~{.php} // Create a `FlatBufferBuilder`, which will be used to create our // monsters' FlatBuffers. $builder = new Google\FlatBuffers\FlatbufferBuilder(1024); ~~~

~~~{.c} flatcc_builder_t builder, *B; B = &builder; // Initialize the builder object. flatcc_builder_init(B); ~~~

~~~{.dart} // Create the fb.Builder object that will be used by our generated builders // Note that if you are only planning to immediately get the byte array this builder would create, // you can use the convenience method `toBytes()` on the generated builders. // For example, you could do something like `new myGame.MonsterBuilder(...).toBytes()` var builder = new fb.Builder(initialSize: 1024); ~~~

~~~{.lua} -- get access to the builder, providing an array of size 1024 local builder = flatbuffers.Builder(1024) ~~~

~~~{.lobster} // get access to the builder let builder = flatbuffers_builder {} ~~~

~~~{.rs} // Build up a serialized buffer algorithmically. // Initialize it with a capacity of 1024 bytes. let mut builder = flatbuffers::FlatBufferBuilder::new_with_capacity(1024); ~~~

~~~{.swift} // create a `FlatBufferBuilder`, which will be used to serialize objects let builder = FlatBufferBuilder(initialSize: 1024) ~~~

After creating the builder, we can start serializing our data. Before we make our orc Monster, let's create some Weapons: a Sword and an Axe.

~~~{.cpp} auto weapon_one_name = builder.CreateString("Sword"); short weapon_one_damage = 3;

auto weapon_two_name = builder.CreateString("Axe"); short weapon_two_damage = 5;

// Use the CreateWeapon shortcut to create Weapons with all the fields set. auto sword = CreateWeapon(builder, weapon_one_name, weapon_one_damage); auto axe = CreateWeapon(builder, weapon_two_name, weapon_two_damage);

</div>
<div class="language-java">
~~~{.java}
  int weaponOneName = builder.createString("Sword")
  short weaponOneDamage = 3;

  int weaponTwoName = builder.createString("Axe");
  short weaponTwoDamage = 5;

  // Use the `createWeapon()` helper function to create the weapons, since we set every field.
  int sword = Weapon.createWeapon(builder, weaponOneName, weaponOneDamage);
  int axe = Weapon.createWeapon(builder, weaponTwoName, weaponTwoDamage);

~~~{.kt} val weaponOneName = builder.createString("Sword") val weaponOneDamage: Short = 3;

val weaponTwoName = builder.createString("Axe") val weaponTwoDamage: Short = 5;

// Use the createWeapon() helper function to create the weapons, since we set every field. val sword = Weapon.createWeapon(builder, weaponOneName, weaponOneDamage) val axe = Weapon.createWeapon(builder, weaponTwoName, weaponTwoDamage)

</div>
<div class="language-csharp">
~~~{.cs}
  var weaponOneName = builder.CreateString("Sword");
  var weaponOneDamage = 3;

  var weaponTwoName = builder.CreateString("Axe");
  var weaponTwoDamage = 5;

  // Use the `CreateWeapon()` helper function to create the weapons, since we set every field.
  var sword = Weapon.CreateWeapon(builder, weaponOneName, (short)weaponOneDamage);
  var axe = Weapon.CreateWeapon(builder, weaponTwoName, (short)weaponTwoDamage);

~~~{.go} weaponOne := builder.CreateString("Sword") weaponTwo := builder.CreateString("Axe")

// Create the first Weapon ("Sword"). sample.WeaponStart(builder) sample.WeaponAddName(builder, weaponOne) sample.WeaponAddDamage(builder, 3) sword := sample.WeaponEnd(builder)

// Create the second Weapon ("Axe"). sample.WeaponStart(builder) sample.WeaponAddName(builder, weaponTwo) sample.WeaponAddDamage(builder, 5) axe := sample.WeaponEnd(builder)

</div>
<div class="language-python">
~~~{.py}
  weapon_one = builder.CreateString('Sword')
  weapon_two = builder.CreateString('Axe')

  # Create the first `Weapon` ('Sword').
  MyGame.Sample.Weapon.Start(builder)
  MyGame.Sample.Weapon.AddName(builder, weapon_one)
  MyGame.Sample.Weapon.AddDamage(builder, 3)
  sword = MyGame.Sample.Weapon.End(builder)

  # Create the second `Weapon` ('Axe').
  MyGame.Sample.Weapon.Start(builder)
  MyGame.Sample.Weapon.AddName(builder, weapon_two)
  MyGame.Sample.Weapon.AddDamage(builder, 5)
  axe = MyGame.Sample.Weapon.End(builder)

~~~{.js} var weaponOne = builder.createString('Sword'); var weaponTwo = builder.createString('Axe');

// Create the first Weapon ('Sword'). MyGame.Sample.Weapon.startWeapon(builder); MyGame.Sample.Weapon.addName(builder, weaponOne); MyGame.Sample.Weapon.addDamage(builder, 3); var sword = MyGame.Sample.Weapon.endWeapon(builder);

// Create the second Weapon ('Axe'). MyGame.Sample.Weapon.startWeapon(builder); MyGame.Sample.Weapon.addName(builder, weaponTwo); MyGame.Sample.Weapon.addDamage(builder, 5); var axe = MyGame.Sample.Weapon.endWeapon(builder);

</div>
<div class="language-typescript">
~~~{.ts}
  let weaponOne = builder.createString('Sword');
  let weaponTwo = builder.createString('Axe');

  // Create the first `Weapon` ('Sword').
  MyGame.Sample.Weapon.startWeapon(builder);
  MyGame.Sample.Weapon.addName(builder, weaponOne);
  MyGame.Sample.Weapon.addDamage(builder, 3);
  let sword = MyGame.Sample.Weapon.endWeapon(builder);

  // Create the second `Weapon` ('Axe').
  MyGame.Sample.Weapon.startWeapon(builder);
  MyGame.Sample.Weapon.addName(builder, weaponTwo);
  MyGame.Sample.Weapon.addDamage(builder, 5);
  let axe = MyGame.Sample.Weapon.endWeapon(builder);

~~~{.php} // Create the `Weapon`s using the `createWeapon()` helper function. $weapon_one_name = $builder->createString("Sword"); $sword = \MyGame\Sample\Weapon::CreateWeapon($builder, $weapon_one_name, 3);

$weapon_two_name = $builder->createString("Axe"); $axe = \MyGame\Sample\Weapon::CreateWeapon($builder, $weapon_two_name, 5);

// Create an array from the two Weapons and pass it to the // CreateWeaponsVector() method to create a FlatBuffer vector. $weaps = array($sword, $axe); $weapons = \MyGame\Sample\Monster::CreateWeaponsVector($builder, $weaps);

</div>
<div class="language-c">
~~~{.c}
  flatbuffers_string_ref_t weapon_one_name = flatbuffers_string_create_str(B, "Sword");
  uint16_t weapon_one_damage = 3;

  flatbuffers_string_ref_t weapon_two_name = flatbuffers_string_create_str(B, "Axe");
  uint16_t weapon_two_damage = 5;

  ns(Weapon_ref_t) sword = ns(Weapon_create(B, weapon_one_name, weapon_one_damage));
  ns(Weapon_ref_t) axe = ns(Weapon_create(B, weapon_two_name, weapon_two_damage));

~~~{.dart} // The generated Builder classes work much like in other languages, final int weaponOneName = builder.writeString("Sword"); final int weaponOneDamage = 3;

final int weaponTwoName = builder.writeString("Axe"); final int weaponTwoDamage = 5;

final swordBuilder = new myGame.WeaponBuilder(builder) ..begin() ..addNameOffset(weaponOneName) ..addDamage(weaponOneDamage); final int sword = swordBuilder.finish();

final axeBuilder = new myGame.WeaponBuilder(builder) ..begin() ..addNameOffset(weaponTwoName) ..addDamage(weaponTwoDamage); final int axe = axeBuilder.finish();

// The generated ObjectBuilder classes offer an easier to use alternative // at the cost of requiring some additional reference allocations. If memory // usage is critical, or if you'll be working with especially large messages // or tables, you should prefer using the generated Builder classes. // The following code would produce an identical buffer as above. final String weaponOneName = "Sword"; final int weaponOneDamage = 3;

final String weaponTwoName = "Axe"; final int weaponTwoDamage = 5;

final myGame.WeaponBuilder sword = new myGame.WeaponObjectBuilder( name: weaponOneName, damage: weaponOneDamage, );

final myGame.WeaponBuilder axe = new myGame.WeaponObjectBuilder( name: weaponTwoName, damage: weaponTwoDamage, );

</div>
<div class="language-lua">
~~~{.lua}
    local weaponOne = builder:CreateString("Sword")
    local weaponTwo = builder:CreateString("Axe")

    -- Create the first 'Weapon'
    weapon.Start(builder)
    weapon.AddName(builder, weaponOne)
    weapon.AddDamage(builder, 3)
    local sword = weapon.End(builder)

    -- Create the second 'Weapon'
    weapon.Start(builder)
    weapon.AddName(builder, weaponTwo)
    weapon.AddDamage(builder, 5)
    local axe = weapon.End(builder)

~~~{.lobster} let weapon_names = [ "Sword", "Axe" ] let weapon_damages = [ 3, 5 ]

let weapon_offsets = map(weapon_names) name, i: let ns = builder.CreateString(name) MyGame_Sample_WeaponBuilder { b } .start() .add_name(ns) .add_damage(weapon_damages[i]) .end()

</div>
<div class="language-rust">
~~~{.rs}
  // Serialize some weapons for the Monster: A 'sword' and an 'axe'.
  let weapon_one_name = builder.create_string("Sword");
  let weapon_two_name = builder.create_string("Axe");

  // Use the `Weapon::create` shortcut to create Weapons with named field
  // arguments.
  let sword = Weapon::create(&mut builder, &WeaponArgs{
      name: Some(weapon_one_name),
      damage: 3,
  });
  let axe = Weapon::create(&mut builder, &WeaponArgs{
      name: Some(weapon_two_name),
      damage: 5,
  });

~~~{.swift} let weapon1Name = builder.create(string: "Sword") let weapon2Name = builder.create(string: "Axe")

// start creating the weapon by calling startWeapon let weapon1Start = Weapon.startWeapon(&builder) Weapon.add(name: weapon1Name, &builder) Weapon.add(damage: 3, &builder) // end the object by passing the start point for the weapon 1 let sword = Weapon.endWeapon(&builder, start: weapon1Start)

let weapon2Start = Weapon.startWeapon(&builder) Weapon.add(name: weapon2Name, &builder) Weapon.add(damage: 5, &builder) let axe = Weapon.endWeapon(&builder, start: weapon2Start)

</div>

Now let's create our monster, the `orc`. For this `orc`, lets make him
`red` with rage, positioned at `(1.0, 2.0, 3.0)`, and give him
a large pool of hit points with `300`. We can give him a vector of weapons
to choose from (our `Sword` and `Axe` from earlier). In this case, we will
equip him with the `Axe`, since it is the most powerful of the two. Lastly,
let's fill his inventory with some potential treasures that can be taken once he
is defeated.

Before we serialize a monster, we need to first serialize any objects that are
contained therein, i.e. we serialize the data tree using depth-first, pre-order
traversal. This is generally easy to do on any tree structures.

<div class="language-cpp">
~~~{.cpp}
  // Serialize a name for our monster, called "Orc".
  auto name = builder.CreateString("Orc");

  // Create a `vector` representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  unsigned char treasure[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
  auto inventory = builder.CreateVector(treasure, 10);

~~~{.java} // Serialize a name for our monster, called "Orc". int name = builder.createString("Orc");

// Create a vector representing the inventory of the Orc. Each number // could correspond to an item that can be claimed after he is slain. byte[] treasure = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; int inv = Monster.createInventoryVector(builder, treasure);

</div>
<div class="language-kotlin">
~~~{.kt}
  // Serialize a name for our monster, called "Orc".
  val name = builder.createString("Orc")

  // Create a `vector` representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  val treasure = byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
  val inv = Monster.createInventoryVector(builder, treasure)

~~~{.cs} // Serialize a name for our monster, called "Orc". var name = builder.CreateString("Orc");

// Create a vector representing the inventory of the Orc. Each number // could correspond to an item that can be claimed after he is slain. // Note: Since we prepend the bytes, this loop iterates in reverse order. Monster.StartInventoryVector(builder, 10); for (int i = 9; i >= 0; i--) { builder.AddByte((byte)i); } var inv = builder.EndVector();

</div>
<div class="language-go">
~~~{.go}
  // Serialize a name for our monster, called "Orc".
  name := builder.CreateString("Orc")

  // Create a `vector` representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  // Note: Since we prepend the bytes, this loop iterates in reverse.
  sample.MonsterStartInventoryVector(builder, 10)
  for i := 9; i >= 0; i-- {
          builder.PrependByte(byte(i))
  }
  inv := builder.EndVector(10)

~~~{.py} # Serialize a name for our monster, called "Orc". name = builder.CreateString("Orc")

Create a vector representing the inventory of the Orc. Each number

could correspond to an item that can be claimed after he is slain.

Note: Since we prepend the bytes, this loop iterates in reverse.

MyGame.Sample.Monster.StartInventoryVector(builder, 10) for i in reversed(range(0, 10)): builder.PrependByte(i) inv = builder.EndVector()

</div>
<div class="language-javascript">
~~~{.js}
  // Serialize a name for our monster, called 'Orc'.
  var name = builder.createString('Orc');

  // Create a `vector` representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  var treasure = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
  var inv = MyGame.Sample.Monster.createInventoryVector(builder, treasure);

~~~{.ts} // Serialize a name for our monster, called 'Orc'. let name = builder.createString('Orc');

// Create a vector representing the inventory of the Orc. Each number // could correspond to an item that can be claimed after he is slain. let treasure = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; let inv = MyGame.Sample.Monster.createInventoryVector(builder, treasure);

</div>
<div class="language-php">
~~~{.php}
  // Serialize a name for our monster, called "Orc".
  $name = $builder->createString("Orc");

  // Create a `vector` representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  $treasure = array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
  $inv = \MyGame\Sample\Monster::CreateInventoryVector($builder, $treasure);

~~~{.c} // Serialize a name for our monster, called "Orc". // The _str suffix indicates the source is an ascii-z string. flatbuffers_string_ref_t name = flatbuffers_string_create_str(B, "Orc");

// Create a vector representing the inventory of the Orc. Each number // could correspond to an item that can be claimed after he is slain. uint8_t treasure[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; flatbuffers_uint8_vec_ref_t inventory; // c_vec_len is the convenience macro we defined earlier. inventory = flatbuffers_uint8_vec_create(B, treasure, c_vec_len(treasure));

</div>
<div class="language-dart">
~~~{.dart}
  // Serialize a name for our monster, called "Orc".
  final int name = builder.writeString('Orc');

  // Create a list representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  final List<int> treasure = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
  final inventory = builder.writeListUint8(treasure);

  // The following code should be used instead if you intend to use the
  // ObjectBuilder classes:
  // Serialize a name for our monster, called "Orc".
  final String name = 'Orc';

  // Create a list representing the inventory of the Orc. Each number
  // could correspond to an item that can be claimed after he is slain.
  final List<int> treasure = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

~~~{.py} -- Serialize a name for our mosnter, called 'orc' local name = builder:CreateString("Orc")

-- Create a `vector` representing the inventory of the Orc. Each number
-- could correspond to an item that can be claimed after he is slain.
-- Note: Since we prepend the bytes, this loop iterates in reverse.
monster.StartInventoryVector(builder, 10)
for i=10,1,-1 do
    builder:PrependByte(i)
end
local inv = builder:EndVector(10)

</div>
<div class="language-lobster">
~~~{.lobster}
  // Name of the monster.
  let name = builder.CreateString("Orc")

  // Inventory.
  let inv = builder.MyGame_Sample_MonsterCreateInventoryVector(map(10): _)

~~~{.rs} // Name of the Monster. let name = builder.create_string("Orc");

// Inventory. let inventory = builder.create_vector(&[0u8, 1, 2, 3, 4, 5, 6, 7, 8, 9]);

</div>
<div class="language-swift">
~~~{.swift}
  // Name of the Monster.
  let name = builder.create(string: "Orc")

  // create inventory
  let inventory: [Byte] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  let inventoryOffset = builder.createVector(inventory)

We serialized two built-in data types (string and vector) and captured their return values. These values are offsets into the serialized data, indicating where they are stored, such that we can refer to them below when adding fields to our monster.

Note: To create a vector of nested objects (e.g. tables, strings, or other vectors), collect their offsets into a temporary data structure, and then create an additional vector containing their offsets.

If instead of creating a vector from an existing array you serialize elements individually one by one, take care to note that this happens in reverse order, as buffers are built back to front.

For example, take a look at the two Weapons that we created earlier (Sword and Axe). These are both FlatBuffer tables, whose offsets we now store in memory. Therefore we can create a FlatBuffer vector to contain these offsets.

~~~{.cpp} // Place the weapons into a `std::vector`, then convert that into a FlatBuffer `vector`. std::vector> weapons_vector; weapons_vector.push_back(sword); weapons_vector.push_back(axe); auto weapons = builder.CreateVector(weapons_vector); ~~~

~~~{.java} // Place the two weapons into an array, and pass it to the `createWeaponsVector()` method to // create a FlatBuffer vector. int[] weaps = new int[2]; weaps[0] = sword; weaps[1] = axe;

// Pass the weaps array into the createWeaponsVector() method to create a FlatBuffer vector. int weapons = Monster.createWeaponsVector(builder, weaps);

</div>
<div class="language-kotlin">
~~~{.kt}
  // Place the two weapons into an array, and pass it to the `createWeaponsVector()` method to
  // create a FlatBuffer vector.
  val weaps = intArrayOf(sword, axe)

  // Pass the `weaps` array into the `createWeaponsVector()` method to create a FlatBuffer vector.
  val weapons = Monster.createWeaponsVector(builder, weaps)

~~~{.cs} var weaps = new Offset[2]; weaps[0] = sword; weaps[1] = axe;

// Pass the weaps array into the CreateWeaponsVector() method to create a FlatBuffer vector. var weapons = Monster.CreateWeaponsVector(builder, weaps);

</div>
<div class="language-go">
~~~{.go}
  // Create a FlatBuffer vector and prepend the weapons.
  // Note: Since we prepend the data, prepend them in reverse order.
  sample.MonsterStartWeaponsVector(builder, 2)
  builder.PrependUOffsetT(axe)
  builder.PrependUOffsetT(sword)
  weapons := builder.EndVector(2)

~~~{.py} # Create a FlatBuffer vector and prepend the weapons. # Note: Since we prepend the data, prepend them in reverse order. MyGame.Sample.Monster.StartWeaponsVector(builder, 2) builder.PrependUOffsetTRelative(axe) builder.PrependUOffsetTRelative(sword) weapons = builder.EndVector() ~~~

~~~{.js} // Create an array from the two `Weapon`s and pass it to the // `createWeaponsVector()` method to create a FlatBuffer vector. var weaps = [sword, axe]; var weapons = MyGame.Sample.Monster.createWeaponsVector(builder, weaps); ~~~

~~~{.ts} // Create an array from the two `Weapon`s and pass it to the // `createWeaponsVector()` method to create a FlatBuffer vector. let weaps = [sword, axe]; let weapons = MyGame.Sample.Monster.createWeaponsVector(builder, weaps); ~~~

~~~{.php} // Create an array from the two `Weapon`s and pass it to the // `CreateWeaponsVector()` method to create a FlatBuffer vector. $weaps = array($sword, $axe); $weapons = \MyGame\Sample\Monster::CreateWeaponsVector($builder, $weaps); ~~~

~~~{.c} // We use the internal builder stack to implement a dynamic vector. ns(Weapon_vec_start(B)); ns(Weapon_vec_push(B, sword)); ns(Weapon_vec_push(B, axe)); ns(Weapon_vec_ref_t) weapons = ns(Weapon_vec_end(B)); ~~~

~~~{.dart} // If using the Builder classes, serialize the `[sword,axe]` final weapons = builder.writeList([sword, axe]);

// If using the ObjectBuilders, just create an array from the two Weapons final List<myGame.WeaponBuilder> weaps = [sword, axe];

</div>
<div class="language-lua">
~~~{.lua}
    -- Create a FlatBuffer vector and prepend the weapons.
    -- Note: Since we prepend the data, prepend them in reverse order.
    monster.StartWeaponsVector(builder, 2)
    builder:PrependUOffsetTRelative(axe)
    builder:PrependUOffsetTRelative(sword)
    local weapons = builder:EndVector(2)

~~~{.lobster} let weapons = builder.MyGame_Sample_MonsterCreateWeaponsVector(weapon_offsets) ~~~

~~~{.rs} // Create a FlatBuffer `vector` that contains offsets to the sword and axe // we created above. let weapons = builder.create_vector(&[sword, axe]); ~~~

~~~{.swift} // Create a FlatBuffer `vector` that contains offsets to the sword and axe // we created above. let weaponsOffset = builder.createVector(ofOffsets: [sword, axe]) ~~~

Note there are additional convenience overloads of `CreateVector`, allowing you to work with data that's not in a `std::vector` or allowing you to generate elements by calling a lambda. For the common case of `std::vector` there's also `CreateVectorOfStrings`.

Note that vectors of structs are serialized differently from tables, since structs are stored in-line in the vector. For example, to create a vector for the path field above:

~~~{.cpp} Vec3 points[] = { Vec3(1.0f, 2.0f, 3.0f), Vec3(4.0f, 5.0f, 6.0f) }; auto path = builder.CreateVectorOfStructs(points, 2); ~~~

~~~{.java} Monster.startPathVector(fbb, 2); Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f); Vec3.createVec3(builder, 4.0f, 5.0f, 6.0f); int path = fbb.endVector(); ~~~

~~~{.kt} Monster.startPathVector(fbb, 2) Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f) Vec3.createVec3(builder, 4.0f, 5.0f, 6.0f) val path = fbb.endVector() ~~~

~~~{.cs} Monster.StartPathVector(fbb, 2); Vec3.CreateVec3(builder, 1.0f, 2.0f, 3.0f); Vec3.CreateVec3(builder, 4.0f, 5.0f, 6.0f); var path = fbb.EndVector(); ~~~

~~~{.go} sample.MonsterStartPathVector(builder, 2) sample.CreateVec3(builder, 1.0, 2.0, 3.0) sample.CreateVec3(builder, 4.0, 5.0, 6.0) path := builder.EndVector(2) ~~~

~~~{.py} MyGame.Sample.Monster.StartPathVector(builder, 2) MyGame.Sample.Vec3.CreateVec3(builder, 1.0, 2.0, 3.0) MyGame.Sample.Vec3.CreateVec3(builder, 4.0, 5.0, 6.0) path = builder.EndVector() ~~~

~~~{.js} MyGame.Sample.Monster.startPathVector(builder, 2); MyGame.Sample.Vec3.createVec3(builder, 1.0, 2.0, 3.0); MyGame.Sample.Vec3.createVec3(builder, 4.0, 5.0, 6.0); var path = builder.endVector(); ~~~

~~~{.ts} MyGame.Sample.Monster.startPathVector(builder, 2); MyGame.Sample.Vec3.createVec3(builder, 1.0, 2.0, 3.0); MyGame.Sample.Vec3.createVec3(builder, 4.0, 5.0, 6.0); let path = builder.endVector(); ~~~

~~~{.php} \MyGame\Example\Monster::StartPathVector($builder, 2); \MyGame\Sample\Vec3::CreateVec3($builder, 1.0, 2.0, 3.0); \MyGame\Sample\Vec3::CreateVec3($builder, 1.0, 2.0, 3.0); $path = $builder->endVector(); ~~~

~~~{.c} // TBD ~~~

~~~{.dart} // Using the Builder classes, you can write a list of structs like so: // Note that the intended order should be reversed if order is important. final vec3Builder = new myGame.Vec3Builder(builder); vec3Builder.finish(4.0, 5.0, 6.0); vec3Builder.finish(1.0, 2.0, 3.0); final int path = builder.endStructVector(2); // the length of the vector

// Otherwise, using the ObjectBuilder classes: // The dart implementation provides a simple interface for writing vectors // of structs, in writeListOfStructs. This method takes // List<ObjectBuilder> and is used by the generated builder classes. final List<myGame.Vec3ObjectBuilder> path = [ new myGame.Vec3ObjectBuilder(x: 1.0, y: 2.0, z: 3.0), new myGame.Vec3ObjectBuilder(x: 4.0, y: 5.0, z: 6.0) ];

</div>
<div class="language-lua">
~~~{.lua}
    -- Create a FlatBuffer vector and prepend the path locations.
    -- Note: Since we prepend the data, prepend them in reverse order.
    monster.StartPathVector(builder, 2)
    vec3.CreateVec3(builder, 1.0, 2.0, 3.0)
    vec3.CreateVec3(builder, 4.0, 5.0, 6.0)
    local path = builder:EndVector(2)

~~~{.lobster} builder.MyGame_Sample_MonsterStartPathVector(2) builder.MyGame_Sample_CreateVec3(1.0, 2.0, 3.0) builder.MyGame_Sample_CreateVec3(4.0, 5.0, 6.0) let path = builder.EndVector(2) ~~~

~~~{.rs} // Create the path vector of Vec3 objects. let x = Vec3::new(1.0, 2.0, 3.0); let y = Vec3::new(4.0, 5.0, 6.0); let path = builder.create_vector(&[x, y]);

// Note that, for convenience, it is also valid to create a vector of // references to structs, like this: // let path = builder.create_vector(&[&x, &y]);

</div>
<div class="language-swift">
~~~{.swift}
  //
  let points = fbb.createVector(ofStructs: [
    Vec3(x: 1, y: 2, z: 3),
    Vec3(x: 4, y: 5, z: 6)
  ])

  // OR
  var vec3 = [
    Vec3(x: 1, y: 2, z: 3),
    Vec3(x: 4, y: 5, z: 6)
  ]
  Monster.startVectorOfVec3(2, in: &fbb)
  for i in obj {
    _ = create(struct: i)
  }
  let points = fbb.endVector(len: size)

We have now serialized the non-scalar components of the orc, so we can serialize the monster itself:

~~~{.cpp} // Create the position struct auto position = Vec3(1.0f, 2.0f, 3.0f);

// Set his hit points to 300 and his mana to 150. int hp = 300; int mana = 150;

// Finally, create the monster using the CreateMonster helper function // to set all fields. auto orc = CreateMonster(builder, &position, mana, hp, name, inventory, Color_Red, weapons, Equipment_Weapon, axe.Union(), path);

</div>
<div class="language-java">
~~~{.java}
  // Create our monster using `startMonster()` and `endMonster()`.
  Monster.startMonster(builder);
  Monster.addPos(builder, Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f));
  Monster.addName(builder, name);
  Monster.addColor(builder, Color.Red);
  Monster.addHp(builder, (short)300);
  Monster.addInventory(builder, inv);
  Monster.addWeapons(builder, weapons);
  Monster.addEquippedType(builder, Equipment.Weapon);
  Monster.addEquipped(builder, axe);
  Monster.addPath(builder, path);
  int orc = Monster.endMonster(builder);

~~~{.kt} // Create our monster using `startMonster()` and `endMonster()`. Monster.startMonster(builder) Monster.addPos(builder, Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f)) Monster.addName(builder, name) Monster.addColor(builder, Color.Red) Monster.addHp(builder, 300.toShort()) Monster.addInventory(builder, inv) Monster.addWeapons(builder, weapons) Monster.addEquippedType(builder, Equipment.Weapon) Monster.addEquipped(builder, axe) Monster.addPath(builder, path) val orc = Monster.endMonster(builder) ~~~

~~~{.cs} // Create our monster using `StartMonster()` and `EndMonster()`. Monster.StartMonster(builder); Monster.AddPos(builder, Vec3.CreateVec3(builder, 1.0f, 2.0f, 3.0f)); Monster.AddHp(builder, (short)300); Monster.AddName(builder, name); Monster.AddInventory(builder, inv); Monster.AddColor(builder, Color.Red); Monster.AddWeapons(builder, weapons); Monster.AddEquippedType(builder, Equipment.Weapon); Monster.AddEquipped(builder, axe.Value); // Axe Monster.AddPath(builder, path); var orc = Monster.EndMonster(builder); ~~~

~~~{.go} // Create our monster using `MonsterStart()` and `MonsterEnd()`. sample.MonsterStart(builder) sample.MonsterAddPos(builder, sample.CreateVec3(builder, 1.0, 2.0, 3.0)) sample.MonsterAddHp(builder, 300) sample.MonsterAddName(builder, name) sample.MonsterAddInventory(builder, inv) sample.MonsterAddColor(builder, sample.ColorRed) sample.MonsterAddWeapons(builder, weapons) sample.MonsterAddEquippedType(builder, sample.EquipmentWeapon) sample.MonsterAddEquipped(builder, axe) sample.MonsterAddPath(builder, path) orc := sample.MonsterEnd(builder) ~~~

~~~{.py} # Create our monster by using `Monster.Start()` and `Monster.End()`. MyGame.Sample.Monster.Start(builder) MyGame.Sample.Monster.AddPos(builder, MyGame.Sample.Vec3.CreateVec3(builder, 1.0, 2.0, 3.0)) MyGame.Sample.Monster.AddHp(builder, 300) MyGame.Sample.Monster.AddName(builder, name) MyGame.Sample.Monster.AddInventory(builder, inv) MyGame.Sample.Monster.AddColor(builder, MyGame.Sample.Color.Color().Red) MyGame.Sample.Monster.AddWeapons(builder, weapons) MyGame.Sample.Monster.AddEquippedType( builder, MyGame.Sample.Equipment.Equipment().Weapon) MyGame.Sample.Monster.AddEquipped(builder, axe) MyGame.Sample.Monster.AddPath(builder, path) orc = MyGame.Sample.Monster.End(builder) ~~~

~~~{.js} // Create our monster by using `startMonster()` and `endMonster()`. MyGame.Sample.Monster.startMonster(builder); MyGame.Sample.Monster.addPos(builder, MyGame.Sample.Vec3.createVec3(builder, 1.0, 2.0, 3.0)); MyGame.Sample.Monster.addHp(builder, 300); MyGame.Sample.Monster.addColor(builder, MyGame.Sample.Color.Red) MyGame.Sample.Monster.addName(builder, name); MyGame.Sample.Monster.addInventory(builder, inv); MyGame.Sample.Monster.addWeapons(builder, weapons); MyGame.Sample.Monster.addEquippedType(builder, MyGame.Sample.Equipment.Weapon); MyGame.Sample.Monster.addEquipped(builder, axe); MyGame.Sample.Monster.addPath(builder, path); var orc = MyGame.Sample.Monster.endMonster(builder); ~~~

~~~{.ts} // Create our monster by using `startMonster()` and `endMonster()`. MyGame.Sample.Monster.startMonster(builder); MyGame.Sample.Monster.addPos(builder, MyGame.Sample.Vec3.createVec3(builder, 1.0, 2.0, 3.0)); MyGame.Sample.Monster.addHp(builder, 300); MyGame.Sample.Monster.addColor(builder, MyGame.Sample.Color.Red) MyGame.Sample.Monster.addName(builder, name); MyGame.Sample.Monster.addInventory(builder, inv); MyGame.Sample.Monster.addWeapons(builder, weapons); MyGame.Sample.Monster.addEquippedType(builder, MyGame.Sample.Equipment.Weapon); MyGame.Sample.Monster.addEquipped(builder, axe); MyGame.Sample.Monster.addPath(builder, path); let orc = MyGame.Sample.Monster.endMonster(builder); ~~~

~~~{.php} // Create our monster by using `StartMonster()` and `EndMonster()`. \MyGame\Sample\Monster::StartMonster($builder); \MyGame\Sample\Monster::AddPos($builder, \MyGame\Sample\Vec3::CreateVec3($builder, 1.0, 2.0, 3.0)); \MyGame\Sample\Monster::AddHp($builder, 300); \MyGame\Sample\Monster::AddName($builder, $name); \MyGame\Sample\Monster::AddInventory($builder, $inv); \MyGame\Sample\Monster::AddColor($builder, \MyGame\Sample\Color::Red); \MyGame\Sample\Monster::AddWeapons($builder, $weapons); \MyGame\Sample\Monster::AddEquippedType($builder, \MyGame\Sample\Equipment::Weapon); \MyGame\Sample\Monster::AddEquipped($builder, $axe); \MyGame\Sample\Monster::AddPath($builder, $path); $orc = \MyGame\Sample\Monster::EndMonster($builder); ~~~

~~~{.c} // Set his hit points to 300 and his mana to 150. uint16_t hp = 300; uint16_t mana = 150;

// Define an equipment union. create calls in C has a single // argument for unions where C++ has both a type and a data argument. ns(Equipment_union_ref_t) equipped = ns(Equipment_as_Weapon(axe)); ns(Vec3_t) pos = { 1.0f, 2.0f, 3.0f }; ns(Monster_create_as_root(B, &pos, mana, hp, name, inventory, ns(Color_Red), weapons, equipped, path));

</div>
<div class="language-dart">
~~~{.dart}
  // Using the Builder API:
  // Set his hit points to 300 and his mana to 150.
  final int hp = 300;
  final int mana = 150;

  final monster = new myGame.MonsterBuilder(builder)
    ..begin()
    ..addNameOffset(name)
    ..addInventoryOffset(inventory)
    ..addWeaponsOffset(weapons)
    ..addEquippedType(myGame.EquipmentTypeId.Weapon)
    ..addEquippedOffset(axe)
    ..addHp(hp)
    ..addMana(mana)
    ..addPos(vec3Builder.finish(1.0, 2.0, 3.0))
    ..addPathOffset(path)
    ..addColor(myGame.Color.Red);

  final int orc = monster.finish();

  // -Or- using the ObjectBuilder API:
  // Set his hit points to 300 and his mana to 150.
  final int hp = 300;
  final int mana = 150;

  // Note that these parameters are optional - it is not necessary to set
  // all of them.
  // Also note that it is not necessary to `finish` the builder helpers above
  // - the generated code will automatically reuse offsets if the same object
  // is used in more than one place (e.g. the axe appearing in `weapons` and
  // `equipped`).
  final myGame.MonsterBuilder orcBuilder = new myGame.MonsterBuilder(
    name: name,
    inventory: treasure,
    weapons: weaps,
    equippedType: myGame.EquipmentTypeId.Weapon,
    equipped: axe,
    path: path,
    hp: hp,
    mana: mana,
    pos: new myGame.Vec3Builder(x: 1.0, y: 2.0, z: 3.0),
    color: myGame.Color.Red,
    path: [
        new myGame.Vec3ObjectBuilder(x: 1.0, y: 2.0, z: 3.0),
        new myGame.Vec3ObjectBuilder(x: 4.0, y: 5.0, z: 6.0)
    ]);

  final int orc = orcBuilder.finish(builder);

~~~{.lua} -- Create our monster by using Start() andEnd() monster.Start(builder) monster.AddPos(builder, vec3.CreateVec3(builder, 1.0, 2.0, 3.0)) monster.AddHp(builder, 300) monster.AddName(builder, name) monster.AddInventory(builder, inv) monster.AddColor(builder, color.Red) monster.AddWeapons(builder, weapons) monster.AddEquippedType(builder, equipment.Weapon) monster.AddEquipped(builder, axe) monster.AddPath(builder, path) local orc = monster.End(builder) ~~~

~~~{.lobster} let orc = MyGame_Sample_MonsterBuilder { b } .start() .add_pos(b.MyGame_Sample_CreateVec3(1.0, 2.0, 3.0)) .add_hp(300) .add_name(name) .add_inventory(inv) .add_color(MyGame_Sample_Color_Red) .add_weapons(weapons) .add_equipped_type(MyGame_Sample_Equipment_Weapon) .add_equipped(weapon_offsets[1]) .add_path(path) .end() ~~~

~~~{.rs} // Create the monster using the `Monster::create` helper function. This // function accepts a `MonsterArgs` struct, which supplies all of the data // needed to build a `Monster`. To supply empty/default fields, just use the // Rust built-in `Default::default()` function, as demonstrated below. let orc = Monster::create(&mut builder, &MonsterArgs{ pos: Some(&Vec3::new(1.0f32, 2.0f32, 3.0f32)), mana: 150, hp: 80, name: Some(name), inventory: Some(inventory), color: Color::Red, weapons: Some(weapons), equipped_type: Equipment::Weapon, equipped: Some(axe.as_union_value()), path: Some(path), ..Default::default() }); ~~~

~~~{.swift} let orc = Monster.createMonster( &builder, pos: MyGame_Sample_Vec3(x: 1, y: 2, z: 3), hp: 300, nameOffset: name, inventoryVectorOffset: inventoryOffset, color: .red, weaponsVectorOffset: weaponsOffset, equippedType: .weapon, equippedOffset: axe) ~~~

Note how we create Vec3 struct in-line in the table. Unlike tables, structs are simple combinations of scalars that are always stored inline, just like scalars themselves.

Important: Unlike structs, you should not nest tables or other objects, which is why we created all the strings/vectors/tables that this monster refers to before start. If you try to create any of them between start and end, you will get an assert/exception/panic depending on your language.

Note: Since we are passing 150 as the mana field, which happens to be the default value, the field will not actually be written to the buffer, since the default value will be returned on query anyway. This is a nice space savings, especially if default values are common in your data. It also means that you do not need to be worried about adding a lot of fields that are only used in a small number of instances, as it will not bloat the buffer if unused.

If you do not wish to set every field in a `table`, it may be more convenient to manually set each field of your monster, instead of calling `CreateMonster()`. The following snippet is functionally equivalent to the above code, but provides a bit more flexibility.
~~~{.cpp} // You can use this code instead of `CreateMonster()`, to create our orc // manually. MonsterBuilder monster_builder(builder); monster_builder.add_pos(&position); monster_builder.add_hp(hp); monster_builder.add_name(name); monster_builder.add_inventory(inventory); monster_builder.add_color(Color_Red); monster_builder.add_weapons(weapons); monster_builder.add_equipped_type(Equipment_Weapon); monster_builder.add_equipped(axe.Union()); auto orc = monster_builder.Finish(); ~~~

If you do not wish to set every field in a `table`, it may be more convenient to manually set each field of your monster, instead of calling `create_monster_as_root()`. The following snippet is functionally equivalent to the above code, but provides a bit more flexibility.
~~~{.c} // It is important to pair `start_as_root` with `end_as_root`. ns(Monster_start_as_root(B)); ns(Monster_pos_create(B, 1.0f, 2.0f, 3.0f)); // or alternatively //ns(Monster_pos_add(&pos);

ns(Monster_hp_add(B, hp)); // Notice that Monser_name_add adds a string reference unlike the // add_str and add_strn variants. ns(Monster_name_add(B, name)); ns(Monster_inventory_add(B, inventory)); ns(Monster_color_add(B, ns(Color_Red))); ns(Monster_weapons_add(B, weapons)); ns(Monster_equipped_add(B, equipped)); // Complete the monster object and make it the buffer root object. ns(Monster_end_as_root(B));

</div>

<div class="language-swift">
~~~{.swift}
  let start = Monster.startMonster(&builder)
  Monster.add(pos: Vec3(x: 1, y: 2, z: 3), &builder)
  Monster.add(hp: 300, &builder)
  Monster.add(name: name, &builder)
  Monster.addVectorOf(inventory: inventoryOffset, &builder)
  Monster.add(color: .red, &builder)
  Monster.addVectorOf(weapons: weaponsOffset, &builder)
  Monster.add(equippedType: .weapon, &builder)
  Monster.add(equipped: axe, &builder)
  var orc = Monster.endMonster(&builder, start: start)

Before finishing the serialization, let's take a quick look at FlatBuffer union Equipped. There are two parts to each FlatBuffer union. The first is a hidden field _type that is generated to hold the type of table referred to by the union. This allows you to know which type to cast to at runtime. Second is the union's data.

In our example, the last two things we added to our Monster were the Equipped Type and the Equipped union itself.

Here is a repetition of these lines, to help highlight them more clearly:

~~~{.cpp} monster_builder.add_equipped_type(Equipment_Weapon); // Union type monster_builder.add_equipped(axe); // Union data ~~~

~~~{.java} Monster.addEquippedType(builder, Equipment.Weapon); // Union type Monster.addEquipped(axe); // Union data ~~~

~~~{.kt} Monster.addEquippedType(builder, Equipment.Weapon) // Union type Monster.addEquipped(axe) // Union data ~~~

~~~{.cs} Monster.AddEquippedType(builder, Equipment.Weapon); // Union type Monster.AddEquipped(builder, axe.Value); // Union data ~~~

~~~{.go} sample.MonsterAddEquippedType(builder, sample.EquipmentWeapon) // Union type sample.MonsterAddEquipped(builder, axe) // Union data ~~~

~~~{.py} MyGame.Sample.Monster.AddEquippedType( # Union type builder, MyGame.Sample.Equipment.Equipment().Weapon) MyGame.Sample.Monster.AddEquipped(builder, axe) # Union data ~~~

~~~{.js} MyGame.Sample.Monster.addEquippedType(builder, MyGame.Sample.Equipment.Weapon); // Union type MyGame.Sample.Monster.addEquipped(builder, axe); // Union data ~~~

~~~{.ts} MyGame.Sample.Monster.addEquippedType(builder, MyGame.Sample.Equipment.Weapon); // Union type MyGame.Sample.Monster.addEquipped(builder, axe); // Union data ~~~

~~~{.php} \MyGame\Sample\Monster::AddEquippedType($builder, \MyGame\Sample\Equipment::Weapon); // Union type \MyGame\Sample\Monster::AddEquipped($builder, $axe); // Union data ~~~

~~~{.c} // Add union type and data simultaneously. ns(Monster_equipped_Weapon_add(B, axe)); ~~~

~~~{.dart} // using the builder API: ..addEquippedType(myGame.EquipmentTypeId.Weapon) ..addEquippedOffset(axe)

// in the ObjectBuilder API: equippedTypeId: myGame.EquipmentTypeId.Weapon, // Union type equipped: axe, // Union data

</div>
<div class="language-lua">
~~~{.lua}
    monster.AddEquippedType(builder, equipment.Weapon) -- Union type
    monster.AddEquipped(builder, axe) -- Union data

~~~{.lobster} .add_equipped_type(MyGame_Sample_Equipment_Weapon) .add_equipped(axe) ~~~

~~~{.rs} // You need to call `as_union_value` to turn an object into a type that // can be used as a union value. monster_builder.add_equipped_type(Equipment::Weapon); // Union type monster_builder.add_equipped(axe.as_union_value()); // Union data ~~~

~~~{.swift} Monster.add(equippedType: .weapon, builder) // Type of union Monster.add(equipped: axe, builder) // Union data ~~~

After you have created your buffer, you will have the offset to the root of the data in the orc variable, so you can finish the buffer by calling the appropriate finish method.

~~~{.cpp} // Call `Finish()` to instruct the builder that this monster is complete. // Note: Regardless of how you created the `orc`, you still need to call // `Finish()` on the `FlatBufferBuilder`. builder.Finish(orc); // You could also call `FinishMonsterBuffer(builder, orc);`. ~~~

~~~{.java} // Call `finish()` to instruct the builder that this monster is complete. builder.finish(orc); // You could also call `Monster.finishMonsterBuffer(builder, orc);`. ~~~

~~~{.kt} // Call `finish()` to instruct the builder that this monster is complete. builder.finish(orc) // You could also call `Monster.finishMonsterBuffer(builder, orc);`. ~~~

~~~{.cs} // Call `Finish()` to instruct the builder that this monster is complete. builder.Finish(orc.Value); // You could also call `Monster.FinishMonsterBuffer(builder, orc);`. ~~~

~~~{.go} // Call `Finish()` to instruct the builder that this monster is complete. builder.Finish(orc) ~~~

~~~{.py} # Call `Finish()` to instruct the builder that this monster is complete. builder.Finish(orc) ~~~

~~~{.js} // Call `finish()` to instruct the builder that this monster is complete. builder.finish(orc); // You could also call `MyGame.Sample.Monster.finishMonsterBuffer(builder, orc);`. ~~~

~~~{.ts} // Call `finish()` to instruct the builder that this monster is complete. builder.finish(orc); // You could also call `MyGame.Sample.Monster.finishMonsterBuffer(builder, orc);`. ~~~

~~~{.php} // Call `finish()` to instruct the builder that this monster is complete. $builder->finish($orc); // You may also call `\MyGame\Sample\Monster::FinishMonsterBuffer($builder, $orc);`. ~~~

~~~{.c} // Because we used `Monster_create_as_root`, we do not need a `finish` call in C`. ~~~

~~~{.dart} // Call `finish()` to instruct the builder that this monster is complete. // See the next code section, as in Dart `finish` will also return the byte array. ~~~

~~~{.lua} -- Call 'Finish()' to instruct the builder that this monster is complete. builder:Finish(orc) ~~~

~~~{.lobster} // Call `Finish()` to instruct the builder that this monster is complete. builder.Finish(orc) ~~~

~~~{.rs} // Call `finish()` to instruct the builder that this monster is complete. builder.finish(orc, None); ~~~

~~~{.swift} // Call `finish(offset:)` to instruct the builder that this monster is complete. builder.finish(offset: orc) ~~~

The buffer is now ready to be stored somewhere, sent over the network, be compressed, or whatever you'd like to do with it. You can access the buffer like so:

~~~{.cpp} // This must be called after `Finish()`. uint8_t *buf = builder.GetBufferPointer(); int size = builder.GetSize(); // Returns the size of the buffer that // `GetBufferPointer()` points to. ~~~

~~~{.java} // This must be called after `finish()`. java.nio.ByteBuffer buf = builder.dataBuffer(); // The data in this ByteBuffer does NOT start at 0, but at buf.position(). // The number of bytes is buf.remaining().

// Alternatively this copies the above data out of the ByteBuffer for you: byte[] buf = builder.sizedByteArray();

</div>
<div class="language-kotlin">
~~~{.kt}
  // This must be called after `finish()`.
  val buf = builder.dataBuffer()
  // The data in this ByteBuffer does NOT start at 0, but at buf.position().
  // The number of bytes is buf.remaining().

  // Alternatively this copies the above data out of the ByteBuffer for you:
  val buf = builder.sizedByteArray()

~~~{.cs} // This must be called after `Finish()`. var buf = builder.DataBuffer; // Of type `FlatBuffers.ByteBuffer`. // The data in this ByteBuffer does NOT start at 0, but at buf.Position. // The end of the data is marked by buf.Length, so the size is // buf.Length - buf.Position.

// Alternatively this copies the above data out of the ByteBuffer for you: byte[] buf = builder.SizedByteArray();

</div>
<div class="language-go">
~~~{.go}
  // This must be called after `Finish()`.
  buf := builder.FinishedBytes() // Of type `byte[]`.

~~~{.py} # This must be called after `Finish()`. buf = builder.Output() // Of type `bytearray`. ~~~

~~~{.js} // This must be called after `finish()`. var buf = builder.asUint8Array(); // Of type `Uint8Array`. ~~~

~~~{.ts} // This must be called after `finish()`. let buf = builder.asUint8Array(); // Of type `Uint8Array`. ~~~

~~~{.php} // This must be called after `finish()`. $buf = $builder->dataBuffer(); // Of type `Google\FlatBuffers\ByteBuffer` // The data in this ByteBuffer does NOT start at 0, but at buf->getPosition(). // The end of the data is marked by buf->capacity(), so the size is // buf->capacity() - buf->getPosition(). ~~~

~~~{.c} uint8_t *buf; size_t size;

// Allocate and extract a readable buffer from internal builder heap. // The returned buffer must be deallocated using free. // NOTE: Finalizing the buffer does NOT change the builder, it // just creates a snapshot of the builder content. buf = flatcc_builder_finalize_buffer(B, &size); // use buf free(buf);

// Optionally reset builder to reuse builder without deallocating // internal stack and heap. flatcc_builder_reset(B); // build next buffer. // ...

// Cleanup. flatcc_builder_clear(B);

</div>
<div class="language-dart">
~~~{.dart}
  final Uint8List buf = builder.finish(orc);

~~~{.lua} -- Get the flatbuffer as a string containing the binary data local bufAsString = builder:Output() ~~~

~~~{.lobster} // This must be called after `Finish()`. let buf = builder.SizedCopy() // Of type `string`. ~~~

~~~{.rs} // This must be called after `finish()`. // `finished_data` returns a byte slice. let buf = builder.finished_data(); // Of type `&[u8]` ~~~

~~~{.swift} // This must be called after `finish()`. // `sizedByteArray` returns the finished buf of type [UInt8]. let buf = builder.sizedByteArray // or you can use to get an object of type Data let bufData = ByteBuffer(data: builder.data) ~~~

Now you can write the bytes to a file or send them over the network. Make sure your file mode (or transfer protocol) is set to BINARY, not text. If you transfer a FlatBuffer in text mode, the buffer will be corrupted, which will lead to hard to find problems when you read the buffer.

For example, in Node you can simply do: ~~~{.js} writeFileSync('monster.bin', buf, 'binary'); ~~~

For example, in Node you can simply do: ~~~{.ts} writeFileSync('monster.bin', buf, 'binary'); ~~~

Reading Orc FlatBuffers

Now that we have successfully created an Orc FlatBuffer, the monster data can be saved, sent over a network, etc. Let's now adventure into the inverse, and access a FlatBuffer.

This section requires the same import/include, namespace, etc. requirements as before:

~~~{.cpp} #include "monster_generated.h" // This was generated by `flatc`.

using namespace MyGame::Sample; // Specified in the schema.

</div>
<div class="language-java">
~~~{.java}
  import MyGame.Sample.*; //The `flatc` generated files. (Monster, Vec3, etc.)

  import com.google.flatbuffers.FlatBufferBuilder;

~~~{.kt} import MyGame.Sample.* //The `flatc` generated files. (Monster, Vec3, etc.)

import com.google.flatbuffers.FlatBufferBuilder

</div>
<div class="language-csharp">
~~~{.cs}
  using FlatBuffers;
  using MyGame.Sample; // The `flatc` generated files. (Monster, Vec3, etc.)

~~~{.go} import ( flatbuffers "github.com/google/flatbuffers/go" sample "MyGame/Sample" ) ~~~

~~~{.py} import flatbuffers

Generated by flatc.

import MyGame.Sample.Any import MyGame.Sample.Color import MyGame.Sample.Monster import MyGame.Sample.Vec3

</div>
<div class="language-javascript">
~~~{.js}
  // The following code is an example - use your desired module flavor by transpiling from TS. 
  var flatbuffers = require('/js/flatbuffers').flatbuffers;
  var MyGame = require('./monster_generated').MyGame; // Generated by `flatc`.

  //--------------------------------------------------------------------------//

  // The following code an example for browser-based HTML/JavaScript. Use the above code
  // for JavaScript module loaders (e.g. Node.js).
  <script src="../js/flatbuffers.js"></script>
  <script src="monster_generated.js"></script> // Generated by `flatc`.

~~~{.ts} // note: import flatbuffers with your desired import method

// note: the ./monster_generated.ts file was previously generated by flatc above using the monster.fbs schema import { MyGame } from './monster_generated';

</div>
<div class="language-php">
~~~{.php}
  // It is recommended that your use PSR autoload when using FlatBuffers in PHP.
  // Here is an example from `SampleBinary.php`:
  function __autoload($class_name) {
    // The last segment of the class name matches the file name.
    $class = substr($class_name, strrpos($class_name, "\\") + 1);
    $root_dir = join(DIRECTORY_SEPARATOR, array(dirname(dirname(__FILE__)))); // `flatbuffers` root.

    // Contains the `*.php` files for the FlatBuffers library and the `flatc` generated files.
    $paths = array(join(DIRECTORY_SEPARATOR, array($root_dir, "php")),
                   join(DIRECTORY_SEPARATOR, array($root_dir, "samples", "MyGame", "Sample")));
    foreach ($paths as $path) {
      $file = join(DIRECTORY_SEPARATOR, array($path, $class . ".php"));
      if (file_exists($file)) {
        require($file);
        break;
      }
    }
  }

~~~{.c} // Only needed if we don't have `#include "monster_builder.h"`. #include "monster_reader.h"

#undef ns #define ns(x) FLATBUFFERS_WRAP_NAMESPACE(MyGame_Sample, x) // Specified in the schema.

</div>
<div class="language-dart">
~~~{.dart}
import 'package:flat_buffers/flat_buffers.dart' as fb;
import './monster_my_game.sample_generated.dart' as myGame;

~~~{.lua} -- require the flatbuffers module local flatbuffers = require("flatbuffers")

-- require the generated files from flatc. local color = require("MyGame.Sample.Color") local equipment = require("MyGame.Sample.Equipment") local monster = require("MyGame.Sample.Monster") local vec3 = require("MyGame.Sample.Vec3") local weapon = require("MyGame.Sample.Weapon")

</div>
<div class="language-lobster">
~~~{.lobster}
  import from "../lobster/"  // Where to find flatbuffers.lobster
  import monster_generated

~~~{.rs} // import the flatbuffers runtime library extern crate flatbuffers;

// import the generated code #[allow(dead_code, unused_imports)] #[path = "./monster_generated.rs"] mod monster_generated; pub use monster_generated::my_game::sample::{get_root_as_monster, Color, Equipment, Monster, MonsterArgs, Vec3, Weapon, WeaponArgs};

</div>

Then, assuming you have a buffer of bytes received from disk,
network, etc., you can start accessing the buffer like so:

**Again, make sure you read the bytes in BINARY mode, otherwise the code below
won't work.**

<div class="language-cpp">
~~~{.cpp}
  uint8_t *buffer_pointer = /* the data you just read */;

  // Get a pointer to the root object inside the buffer.
  auto monster = GetMonster(buffer_pointer);

  // `monster` is of type `Monster *`.
  // Note: root object pointers are NOT the same as `buffer_pointer`.
  // `GetMonster` is a convenience function that calls `GetRoot<Monster>`,
  // the latter is also available for non-root types.

~~~{.java} byte[] bytes = /* the data you just read */ java.nio.ByteBuffer buf = java.nio.ByteBuffer.wrap(bytes);

// Get an accessor to the root object inside the buffer. Monster monster = Monster.getRootAsMonster(buf);

</div>
<div class="language-kotlin">
~~~{.kt}
  val bytes = /* the data you just read */
  val buf = java.nio.ByteBuffer.wrap(bytes)

  // Get an accessor to the root object inside the buffer.
  Monster monster = Monster.getRootAsMonster(buf)

~~~{.cs} byte[] bytes = /* the data you just read */ var buf = new ByteBuffer(bytes);

// Get an accessor to the root object inside the buffer. var monster = Monster.GetRootAsMonster(buf);

</div>
<div class="language-go">
~~~{.go}
  var buf []byte = /* the data you just read */

  // Get an accessor to the root object inside the buffer.
  monster := sample.GetRootAsMonster(buf, 0)

  // Note: We use `0` for the offset here, which is typical for most buffers
  // you would read. If you wanted to read from `builder.Bytes` directly, you
  // would need to pass in the offset of `builder.Head()`, as the builder
  // constructs the buffer backwards, so may not start at offset 0.

~~~{.py} buf = /* the data you just read, in an object of type "bytearray" */

// Get an accessor to the root object inside the buffer. monster = MyGame.Sample.Monster.Monster.GetRootAs(buf, 0)

Note: We use 0 for the offset here, which is typical for most buffers

you would read. If you wanted to read from the builder.Bytes directly,

you would need to pass in the offset of builder.Head(), as the builder

constructs the buffer backwards, so may not start at offset 0.

</div>
<div class="language-javascript">
~~~{.js}
  // the data you just read, as a `Uint8Array`
  // Note that the example here uses `readFileSync` from the built-in `fs` module,
  // but other methods for accessing the file contents will also work.
  var bytes = new Uint8Array(readFileSync('./monsterdata.bin'));

  var buf = new flatbuffers.ByteBuffer(bytes);

  // Get an accessor to the root object inside the buffer.
  var monster = MyGame.Sample.Monster.getRootAsMonster(buf);

~~~{.ts} // the data you just read, as a `Uint8Array`. // Note that the example here uses `readFileSync` from the built-in `fs` module, // but other methods for accessing the file contents will also work. let bytes = new Uint8Array(readFileSync('./monsterdata.bin'));

let buf = new flatbuffers.ByteBuffer(bytes);

// Get an accessor to the root object inside the buffer. let monster = MyGame.Sample.Monster.getRootAsMonster(buf);

</div>
<div class="language-php">
~~~{.php}
  $bytes = /* the data you just read, in a string */
  $buf = Google\FlatBuffers\ByteBuffer::wrap($bytes);

  // Get an accessor to the root object inside the buffer.
  $monster = \MyGame\Sample\Monster::GetRootAsMonster($buf);

~~~{.c} // Note that we use the `table_t` suffix when reading a table object // as opposed to the `ref_t` suffix used during the construction of // the buffer. ns(Monster_table_t) monster = ns(Monster_as_root(buffer));

// Note: root object pointers are NOT the same as the buffer pointer.

</div>
<div class="language-dart">
~~~{.dart}
List<int> data = ... // the data, e.g. from file or network
// A generated factory constructor that will read the data.
myGame.Monster monster = new myGame.Monster(data);

~~~{.lua} local bufAsString = -- The data you just read in

-- Convert the string representation into binary array Lua structure
local buf = flatbuffers.binaryArray.New(bufAsString)

-- Get an accessor to the root object insert the buffer
local mon = monster.GetRootAsMonster(buf, 0)

</div>
<div class="language-lobster">
~~~{.lobster}
  buf = /* the data you just read, in a string */

  // Get an accessor to the root object inside the buffer.
  let monster = MyGame_Sample_GetRootAsMonster(buf)

~~~{.rs} let buf = /* the data you just read, in a &[u8] */

// Get an accessor to the root object inside the buffer. let monster = get_root_as_monster(buf);

</div>
<div class="language-swift">
~~~{.swift}
  // create a ByteBuffer(:) from an [UInt8] or Data()
  let buf = // Get your data

  // Get an accessor to the root object inside the buffer.
  let monster = Monster.getRootAsMonster(bb: ByteBuffer(bytes: buf))

If you look in the generated files from the schema compiler, you will see it generated accessors for all non-deprecated fields. For example:

~~~{.cpp} auto hp = monster->hp(); auto mana = monster->mana(); auto name = monster->name()->c_str(); ~~~

~~~{.java} short hp = monster.hp(); short mana = monster.mana(); String name = monster.name(); ~~~

~~~{.kt} val hp = monster.hp val mana = monster.mana val name = monster.name ~~~

~~~{.cs} // For C#, unlike most other languages support by FlatBuffers, most values (except for // vectors and unions) are available as properties instead of accessor methods. var hp = monster.Hp var mana = monster.Mana var name = monster.Name ~~~

~~~{.go} hp := monster.Hp() mana := monster.Mana() name := string(monster.Name()) // Note: `monster.Name()` returns a byte[]. ~~~

~~~{.py} hp = monster.Hp() mana = monster.Mana() name = monster.Name() ~~~

~~~{.js} var hp = monster.hp(); var mana = monster.mana(); var name = monster.name(); ~~~

~~~{.ts} let hp = monster.hp(); let mana = monster.mana(); let name = monster.name(); ~~~

~~~{.php} $hp = $monster->getHp(); $mana = $monster->getMana(); $name = monster->getName(); ~~~

~~~{.c} uint16_t hp = ns(Monster_hp(monster)); uint16_t mana = ns(Monster_mana(monster)); flatbuffers_string_t name = ns(Monster_name(monster)); ~~~

~~~{.dart} // For Dart, unlike other languages support by FlatBuffers, most values // are available as properties instead of accessor methods. var hp = monster.hp; var mana = monster.mana; var name = monster.name; ~~~

~~~{.lua} local hp = mon:Hp() local mana = mon:Mana() local name = mon:Name() ~~~

~~~{.lobster} let hp = monster.hp let mana = monster.mana let name = monster.name ~~~

~~~{.rs} // Get and test some scalar types from the FlatBuffer. let hp = monster.hp(); let mana = monster.mana(); let name = monster.name(); ~~~

~~~{.swift} let hp = monster.hp let mana = monster.mana let name = monster.name // returns an optional string ~~~

These should hold 300, 150, and "Orc" respectively.

Note: The default value 150 wasn't stored in mana, but we are still able to retrieve it.

To access sub-objects, in the case of our pos, which is a Vec3:

~~~{.cpp} auto pos = monster->pos(); auto x = pos->x(); auto y = pos->y(); auto z = pos->z(); ~~~

~~~{.java} Vec3 pos = monster.pos(); float x = pos.x(); float y = pos.y(); float z = pos.z(); ~~~

~~~{.kt} val pos = monster.pos!! val x = pos.x val y = pos.y val z = pos.z ~~~

~~~{.cs} var pos = monster.Pos.Value; var x = pos.X; var y = pos.Y; var z = pos.Z; ~~~

~~~{.go} pos := monster.Pos(nil) x := pos.X() y := pos.Y() z := pos.Z()

// Note: Whenever you access a new object, like in Pos(), a new temporary // accessor object gets created. If your code is very performance sensitive, // you can pass in a pointer to an existing Vec3 instead of nil. This // allows you to reuse it across many calls to reduce the amount of object // allocation/garbage collection.

</div>
<div class="language-python">
~~~{.py}
  pos = monster.Pos()
  x = pos.X()
  y = pos.Y()
  z = pos.Z()

~~~{.js} var pos = monster.pos(); var x = pos.x(); var y = pos.y(); var z = pos.z(); ~~~

~~~{.ts} let pos = monster.pos(); let x = pos.x(); let y = pos.y(); let z = pos.z(); ~~~

~~~{.php} $pos = $monster->getPos(); $x = $pos->getX(); $y = $pos->getY(); $z = $pos->getZ(); ~~~

~~~{.c} ns(Vec3_struct_t) pos = ns(Monster_pos(monster)); float x = ns(Vec3_x(pos)); float y = ns(Vec3_y(pos)); float z = ns(Vec3_z(pos)); ~~~

~~~{.dart} myGame.Vec3 pos = monster.pos; double x = pos.x; double y = pos.y; double z = pos.z; ~~~

~~~{.lua} local pos = mon:Pos() local x = pos:X() local y = pos:Y() local z = pos:Z() ~~~

~~~{.lobster} let pos = monster.pos let x = pos.x let y = pos.y let z = pos.z ~~~

~~~{.rs} let pos = monster.pos().unwrap(); let x = pos.x(); let y = pos.y(); let z = pos.z(); ~~~

~~~{.swift} let pos = monster.pos let x = pos.x let y = pos.y let z = pos.z ~~~

x, y, and z will contain 1.0, 2.0, and 3.0, respectively.

Note: Had we not set pos during serialization, it would be a null-value.

Similarly, we can access elements of the inventory vector by indexing it. You can also iterate over the length of the array/vector representing the FlatBuffers vector.

~~~{.cpp} auto inv = monster->inventory(); // A pointer to a `flatbuffers::Vector<>`. auto inv_len = inv->size(); auto third_item = inv->Get(2); ~~~

~~~{.java} int invLength = monster.inventoryLength(); byte thirdItem = monster.inventory(2); ~~~

~~~{.kotlin} val invLength = monster.inventoryLength val thirdItem = monster.inventory(2)!! ~~~

~~~{.cs} int invLength = monster.InventoryLength; var thirdItem = monster.Inventory(2); ~~~

~~~{.go} invLength := monster.InventoryLength() thirdItem := monster.Inventory(2) ~~~

~~~{.py} inv_len = monster.InventoryLength() third_item = monster.Inventory(2) ~~~

~~~{.js} var invLength = monster.inventoryLength(); var thirdItem = monster.inventory(2); ~~~

~~~{.ts} let invLength = monster.inventoryLength(); let thirdItem = monster.inventory(2); ~~~

~~~{.php} $inv_len = $monster->getInventoryLength(); $third_item = $monster->getInventory(2); ~~~

~~~{.c} // If `inv` hasn't been set, it will be null. It is valid get // the length of null which will be 0, useful for iteration. flatbuffers_uint8_vec_t inv = ns(Monster_inventory(monster)); size_t inv_len = flatbuffers_uint8_vec_len(inv); ~~~

~~~{.dart} int invLength = monster.inventory.length; var thirdItem = monster.inventory[2]; ~~~

~~~{.lua} local invLength = mon:InventoryLength() local thirdItem = mon:Inventory(3) -- Lua is 1-based ~~~

~~~{.lobster} let inv_len = monster.inventory_length let third_item = monster.inventory(2) ~~~

~~~{.rs} // Get and test an element from the `inventory` FlatBuffer's `vector`. let inv = monster.inventory().unwrap();

// Note that this vector is returned as a slice, because direct access for // this type, a u8 vector, is safe on all platforms: let third_item = inv[2];

</div>
<div class="language-swift">
~~~{.swift}
  // Get a the count of objects in the vector
  let count = monster.inventoryCount

  // get item at index 4
  let object = monster.inventory(at: 4)

  // or you can fetch the entire array
  let inv = monster.inventory
  // inv[4] should equal object

For vectors of tables, you can access the elements like any other vector, except you need to handle the result as a FlatBuffer table:

~~~{.cpp} auto weapons = monster->weapons(); // A pointer to a `flatbuffers::Vector<>`. auto weapon_len = weapons->size(); auto second_weapon_name = weapons->Get(1)->name()->str(); auto second_weapon_damage = weapons->Get(1)->damage() ~~~

~~~{.java} int weaponsLength = monster.weaponsLength(); String secondWeaponName = monster.weapons(1).name(); short secondWeaponDamage = monster.weapons(1).damage(); ~~~

~~~{.kt} val weaponsLength = monster.weaponsLength val secondWeaponName = monster.weapons(1)!!.name val secondWeaponDamage = monster.weapons(1)!!.damage ~~~

~~~{.cs} int weaponsLength = monster.WeaponsLength; var secondWeaponName = monster.Weapons(1).Name; var secondWeaponDamage = monster.Weapons(1).Damage; ~~~

~~~{.go} weaponLength := monster.WeaponsLength() weapon := new(sample.Weapon) // We need a `sample.Weapon` to pass into `monster.Weapons()` // to capture the output of the function. if monster.Weapons(weapon, 1) { secondWeaponName := weapon.Name() secondWeaponDamage := weapon.Damage() } ~~~

~~~{.py} weapons_length = monster.WeaponsLength() second_weapon_name = monster.Weapons(1).Name() second_weapon_damage = monster.Weapons(1).Damage() ~~~

~~~{.js} var weaponsLength = monster.weaponsLength(); var secondWeaponName = monster.weapons(1).name(); var secondWeaponDamage = monster.weapons(1).damage(); ~~~

~~~{.ts} let weaponsLength = monster.weaponsLength(); let secondWeaponName = monster.weapons(1).name(); let secondWeaponDamage = monster.weapons(1).damage(); ~~~

~~~{.php} $weapons_len = $monster->getWeaponsLength(); $second_weapon_name = $monster->getWeapons(1)->getName(); $second_weapon_damage = $monster->getWeapons(1)->getDamage(); ~~~

~~~{.c} ns(Weapon_vec_t) weapons = ns(Monster_weapons(monster)); size_t weapons_len = ns(Weapon_vec_len(weapons)); // We can use `const char *` instead of `flatbuffers_string_t`. const char *second_weapon_name = ns(Weapon_name(ns(Weapon_vec_at(weapons, 1)))); uint16_t second_weapon_damage = ns(Weapon_damage(ns(Weapon_vec_at(weapons, 1)))); ~~~

~~~{.dart} int weaponsLength = monster.weapons.length; var secondWeaponName = monster.weapons[1].name; var secondWeaponDamage = monster.Weapons[1].damage; ~~~

~~~{.lua} local weaponsLength = mon:WeaponsLength() local secondWeaponName = mon:Weapon(2):Name() local secondWeaponDamage = mon:Weapon(2):Damage() ~~~

~~~{.lobster} let weapons_length = monster.weapons_length let second_weapon_name = monster.weapons(1).name let second_weapon_damage = monster.weapons(1).damage ~~~

~~~{.rs} // Get and test the `weapons` FlatBuffers's `vector`. let weps = monster.weapons().unwrap(); let weps_len = weps.len();

let wep2 = weps.get(1); let second_weapon_name = wep2.name(); let second_weapon_damage = wep2.damage();

</div>
<div class="language-swift">
~~~{.swift}
  // Get the count of weapon objects
  let wepsCount = monster.weaponsCount

  let weapon2 = monster.weapons(at: 1)
  let weaponName = weapon2.name
  let weaponDmg = weapon2.damage

Last, we can access our Equipped FlatBuffer union. Just like when we created the union, we need to get both parts of the union: the type and the data.

We can access the type to dynamically cast the data as needed (since the union only stores a FlatBuffer table).

~~~{.cpp} auto union_type = monster.equipped_type();

if (union_type == Equipment_Weapon) { auto weapon = static_cast<const Weapon*>(monster->equipped()); // Requires static_cast // to type const Weapon*.

auto weapon_name = weapon->name()->str(); // "Axe"
auto weapon_damage = weapon->damage();    // 5

}

</div>
<div class="language-java">
~~~{.java}
  int unionType = monster.EquippedType();

  if (unionType == Equipment.Weapon) {
    Weapon weapon = (Weapon)monster.equipped(new Weapon()); // Requires explicit cast
                                                            // to `Weapon`.

    String weaponName = weapon.name();    // "Axe"
    short weaponDamage = weapon.damage(); // 5
  }

~~~{.kt} val unionType = monster.EquippedType

if (unionType == Equipment.Weapon) { val weapon = monster.equipped(Weapon()) as Weapon // Requires explicit cast // to Weapon.

val weaponName = weapon.name   // "Axe"
val weaponDamage = weapon.damage // 5

}

</div>
<div class="language-csharp">
~~~{.cs}
  var unionType = monster.EquippedType;

  if (unionType == Equipment.Weapon) {
    var weapon = monster.Equipped<Weapon>().Value;

    var weaponName = weapon.Name;     // "Axe"
    var weaponDamage = weapon.Damage; // 5
  }

~~~{.go} // We need a `flatbuffers.Table` to capture the output of the // `monster.Equipped()` function. unionTable := new(flatbuffers.Table)

if monster.Equipped(unionTable) { unionType := monster.EquippedType()

      if unionType == sample.EquipmentWeapon {
              // Create a `sample.Weapon` object that can be initialized with the contents
              // of the `flatbuffers.Table` (`unionTable`), which was populated by
              // `monster.Equipped()`.
              unionWeapon = new(sample.Weapon)
              unionWeapon.Init(unionTable.Bytes, unionTable.Pos)

              weaponName = unionWeapon.Name()
              weaponDamage = unionWeapon.Damage()
      }

}

</div>
<div class="language-python">
~~~{.py}
  union_type = monster.EquippedType()

  if union_type == MyGame.Sample.Equipment.Equipment().Weapon:
    # `monster.Equipped()` returns a `flatbuffers.Table`, which can be used to
    # initialize a `MyGame.Sample.Weapon.Weapon()`.
    union_weapon = MyGame.Sample.Weapon.Weapon()
    union_weapon.Init(monster.Equipped().Bytes, monster.Equipped().Pos)

    weapon_name = union_weapon.Name()     // 'Axe'
    weapon_damage = union_weapon.Damage() // 5

~~~{.js} var unionType = monster.equippedType();

if (unionType == MyGame.Sample.Equipment.Weapon) { var weaponName = monster.equipped(new MyGame.Sample.Weapon()).name(); // 'Axe' var weaponDamage = monster.equipped(new MyGame.Sample.Weapon()).damage(); // 5 }

</div>
<div class="language-typescript">
~~~{.ts}
  let unionType = monster.equippedType();

  if (unionType == MyGame.Sample.Equipment.Weapon) {
    let weaponName = monster.equipped(new MyGame.Sample.Weapon()).name();     // 'Axe'
    let weaponDamage = monster.equipped(new MyGame.Sample.Weapon()).damage(); // 5
  }

~~~{.php} $union_type = $monster->getEquippedType();

if ($union_type == \MyGame\Sample\Equipment::Weapon) { $weapon_name = $monster->getEquipped(new \MyGame\Sample\Weapon())->getName(); // "Axe" $weapon_damage = $monster->getEquipped(new \MyGame\Sample\Weapon())->getDamage(); // 5 }

</div>
<div class="language-c">
~~~{.c}
  // Access union type field.
  if (ns(Monster_equipped_type(monster)) == ns(Equipment_Weapon)) {
      // Cast to appropriate type:
      // C allows for silent void pointer assignment, so we need no explicit cast.
      ns(Weapon_table_t) weapon = ns(Monster_equipped(monster));
      const char *weapon_name = ns(Weapon_name(weapon)); // "Axe"
      uint16_t weapon_damage = ns(Weapon_damage(weapon)); // 5
  }

~~~{.dart} var unionType = monster.equippedType.value;

if (unionType == myGame.EquipmentTypeId.Weapon.value) { myGame.Weapon weapon = mon.equipped as myGame.Weapon;

var weaponName = weapon.name;     // "Axe"
var weaponDamage = weapon.damage; // 5

}

</div>
<div class="language-lua">
~~~{.lua}
  local unionType = mon:EquippedType()

  if unionType == equipment.Weapon then
    local unionWeapon = weapon.New()
    unionWeapon:Init(mon:Equipped().bytes, mon:Equipped().pos)

    local weaponName = unionWeapon:Name()     -- 'Axe'
    local weaponDamage = unionWeapon:Damage() -- 5
  end

~~~{.lobster} union_type = monster.equipped_type

if union_type == MyGame_Sample_Equipment_Weapon: // monster.equipped_as_Weapon returns a FlatBuffer handle much like normal table fields, // but this is only valid to call if we already know it is the correct type. let union_weapon = monster.equipped_as_Weapon

  let weapon_name = union_weapon.name     // "Axe"
  let weapon_damage = union_weapon.damage // 5

</div>
<div class="language-rust">
~~~{.rs}
  // Get and test the `Equipment` union (`equipped` field).
  // `equipped_as_weapon` returns a FlatBuffer handle much like normal table
  // fields, but this will return `None` if the union is not actually of that
  // type.
  if monster.equipped_type() == Equipment::Weapon {
    let equipped = monster.equipped_as_weapon().unwrap();
    let weapon_name = equipped.name();
    let weapon_damage = equipped.damage();

~~~{.swift} // Get and check if the monster has an equipped item if monster.equippedType == .weapon { let _weapon = monster.equipped(type: Weapon.self) let name = _weapon.name // should return "Axe" let dmg = _weapon.damage // should return 5 } ~~~

Mutating FlatBuffers

As you saw above, typically once you have created a FlatBuffer, it is read-only from that moment on. There are, however, cases where you have just received a FlatBuffer, and you'd like to modify something about it before sending it on to another recipient. With the above functionality, you'd have to generate an entirely new FlatBuffer, while tracking what you modified in your own data structures. This is inconvenient.

For this reason FlatBuffers can also be mutated in-place. While this is great for making small fixes to an existing buffer, you generally want to create buffers from scratch whenever possible, since it is much more efficient and the API is much more general purpose.

To get non-const accessors, invoke flatc with --gen-mutable.

Similar to how we read fields using the accessors above, we can now use the mutators like so:

~~~{.cpp} auto monster = GetMutableMonster(buffer_pointer); // non-const monster->mutate_hp(10); // Set the table `hp` field. monster->mutable_pos()->mutate_z(4); // Set struct field. monster->mutable_inventory()->Mutate(0, 1); // Set vector element. ~~~

~~~{.java} Monster monster = Monster.getRootAsMonster(buf); monster.mutateHp(10); // Set table field. monster.pos().mutateZ(4); // Set struct field. monster.mutateInventory(0, 1); // Set vector element. ~~~

~~~{.kt} val monster = Monster.getRootAsMonster(buf) monster.mutateHp(10) // Set table field. monster.pos!!.mutateZ(4) // Set struct field. monster.mutateInventory(0, 1) // Set vector element. ~~~

~~~{.cs} var monster = Monster.GetRootAsMonster(buf); monster.MutateHp(10); // Set table field. monster.Pos.MutateZ(4); // Set struct field. monster.MutateInventory(0, 1); // Set vector element. ~~~

~~~{.go} ~~~

~~~{.py} ~~~

~~~{.js} ~~~

~~~{.ts} ~~~

~~~{.php} ~~~

~~~{.c} ~~~

~~~{.dart} ~~~

~~~{.lua} ~~~

~~~{.lobster} ~~~

~~~{.rs} ~~~

~~~{.swift} let monster = Monster.getRootAsMonster(bb: ByteBuffer(bytes: buf)) monster.mutate(hp: 10) // mutates a value in a table /// to mutate structs in swift you have to use the mutable accessors monster.mutablePos.mutate(z: 4) // mutates a value in a struct monster.mutate(inventory: 6, at index: 0) // mutates a value in an Scalar array ~~~

We use the somewhat verbose term mutate instead of set to indicate that this is a special use case, not to be confused with the default way of constructing FlatBuffer data.

After the above mutations, you can send on the FlatBuffer to a new recipient without any further work!

Note that any mutate functions on a table will return a boolean, which is false if the field we're trying to set is not present in the buffer. Fields are not present if they weren't set, or even if they happen to be equal to the default value. For example, in the creation code above, the mana field is equal to 150, which is the default value, so it was never stored in the buffer. Trying to call the corresponding mutate method for mana on such data will return false, and the value won't actually be modified!

One way to solve this is to call ForceDefaults on a FlatBufferBuilder to force all fields you set to actually be written. This, of course, increases the size of the buffer somewhat, but this may be acceptable for a mutable buffer.

If this is not sufficient, other ways of mutating FlatBuffers may be supported in your language through an object based API (--gen-object-api) or reflection. See the individual language documents for support.

Using flatc as a JSON Conversion Tool

If you are working with C, C++, or Lobster, you can parse JSON at runtime. If your language does not support JSON at the moment, flatc may provide an alternative. Using flatc is often the preferred method, as it doesn't require you to add any new code to your program. It is also efficient, since you can ship with the binary data. The drawback is that it requires an extra step for your users/developers to perform (although it may be able to be automated as part of your compilation).

JSON to binary representation

Let's say you have a JSON file that describes your monster. In this example, we will use the file flatbuffers/samples/monsterdata.json.

Here are the contents of the file:

{
  "pos": {
    "x": 1.0,
    "y": 2.0,
    "z": 3.0
  },
  "hp": 300,
  "name": "Orc",
  "weapons": [
    {
      "name": "axe",
      "damage": 100
    },
    {
      "name": "bow",
      "damage": 90
    }
  ],
  "equipped_type": "Weapon",
  "equipped": {
    "name": "bow",
    "damage": 90
  }
}

You can run this file through the flatc compiler with the -b flag and our monster.fbs schema to produce a FlatBuffer binary file.

./../flatc --binary monster.fbs monsterdata.json

The output of this will be a file monsterdata.bin, which will contain the FlatBuffer binary representation of the contents from our .json file.

*Note: If you're working in C++, you can also parse JSON at runtime. See the [Use in C++](@ref flatbuffers_guide_use_cpp) section of the Programmer's Guide for more information.*

*Note: If you're working in C, the `flatcc --json` (not `flatc`) compiler will generate schema specific high performance json parsers and printers that you can compile and use at runtime. The `flatc` compiler (not `flatcc`) on the other hand, is still useful for general offline json to flatbuffer conversion from a given schema. There are no current plans for `flatcc` to support this.*

*Note: If you're working in Lobster, you can also parse JSON at runtime. See the [Use in Lobster](@ref flatbuffers_guide_use_lobster) section of the Programmer's Guide for more information.*

FlatBuffer binary to JSON

Converting from a FlatBuffer binary representation to JSON is supported as well:

./../flatc --json --raw-binary monster.fbs -- monsterdata.bin

This will convert monsterdata.bin back to its original JSON representation. You need to pass the corresponding FlatBuffers schema so that flatc knows how to interpret the binary buffer. Since monster.fbs does not specify an explicit file_identifier for binary buffers, flatc needs to be forced into reading the .bin file using the --raw-binary option.

The FlatBuffer binary representation does not explicitly encode default values, therefore they are not present in the resulting JSON unless you specify --defaults-json.

If you intend to process the JSON with other tools, you may consider switching on --strict-json so that identifiers are quoted properly.

Note: The resulting JSON file is not necessarily identical with the original JSON. If the binary representation contains floating point numbers, floats and doubles are rounded to 6 and 12 digits, respectively, in order to represent them as decimals in the JSON document.

Advanced Features for Each Language

Each language has a dedicated Use in XXX page in the Programmer's Guide to cover the nuances of FlatBuffers in that language.

For your chosen language, see:

[Use in C++](@ref flatbuffers_guide_use_cpp)

[Use in Java](@ref flatbuffers_guide_use_java)

[Use in Kotlin](@ref flatbuffers_guide_use_kotlin)

[Use in C#](@ref flatbuffers_guide_use_c-sharp)

[Use in Go](@ref flatbuffers_guide_use_go)

[Use in Python](@ref flatbuffers_guide_use_python)

[Use in JavaScript](@ref flatbuffers_guide_use_javascript)

[Use in TypeScript](@ref flatbuffers_guide_use_typescript)

[Use in PHP](@ref flatbuffers_guide_use_php)

[Use in C](@ref flatbuffers_guide_use_c)

[Use in Dart](@ref flatbuffers_guide_use_dart)

[Use in Lua](@ref flatbuffers_guide_use_lua)

[Use in Lobster](@ref flatbuffers_guide_use_lobster)

[Use in Rust](@ref flatbuffers_guide_use_rust)

[Use in Swift](@ref flatbuffers_guide_use_swift)