112 lines
3.4 KiB
ReStructuredText
112 lines
3.4 KiB
ReStructuredText
.. _app_component_tree:
|
|
|
|
###################
|
|
App Component Tree
|
|
###################
|
|
|
|
**Audience:** Users who want to know how components can be composed with each other.
|
|
|
|
**Level:** Basic
|
|
|
|
----
|
|
|
|
**************************************
|
|
What is an Application Component Tree?
|
|
**************************************
|
|
|
|
Components can be nested to form component trees where the LightningFlows are its branches and LightningWorks are its leaves.
|
|
|
|
This design enables users to organize and maintain their code with more ease, but more importantly, this helps creating an ecosystem with re-usable components.
|
|
|
|
Here's a basic application with four flows and two works (associated tree structure):
|
|
|
|
.. figure:: https://pl-flash-data.s3.amazonaws.com/assets_lightning/tree.gif
|
|
:alt: Basic App Components
|
|
:width: 100 %
|
|
|
|
|
|
.. literalinclude:: ../code_samples/quickstart/app_comp.py
|
|
|
|
A Lightning app runs all flows into a single process. Its flows coordinate the execution of the works each running in their own independent processes.
|
|
|
|
----
|
|
|
|
***********************************************
|
|
How do I define my application component tree?
|
|
***********************************************
|
|
|
|
In order to define your application component tree, you need create a tree of components and attach them to your root flow.
|
|
|
|
You can attach your components in the **__init__** method of a flow.
|
|
|
|
.. code-block:: python
|
|
|
|
import lightning as L
|
|
|
|
|
|
class RootFlow(L.LightningFlow):
|
|
def __init__(self):
|
|
super().__init__()
|
|
# The `Work` component is attached here.
|
|
self.work = Work()
|
|
|
|
# The `NestedFlow` component is attached here.
|
|
self.nested_flow = NestedFlow()
|
|
|
|
Once done, simply add the root flow to a Lightning app as follows:
|
|
|
|
.. code-block:: python
|
|
|
|
app = L.LightningApp(RootFlow())
|
|
|
|
----
|
|
|
|
******************************************
|
|
Is my application component tree static?
|
|
******************************************
|
|
|
|
No, Lightning supports dynamic flows and works.
|
|
|
|
You can simply attach your components in the **run** method of a flow using the Python functions **hasattr**, **setattr**, and **getattr**.
|
|
|
|
.. code-block:: python
|
|
|
|
class RootFlow(L.LightningFlow):
|
|
def run(self):
|
|
|
|
if not hasattr(self, "work"):
|
|
# The `Work` component is attached here.
|
|
setattr(self, "work", Work())
|
|
# Run the `Work` component.
|
|
getattr(self, "work").run()
|
|
|
|
if not hasattr(self, "nested_flow"):
|
|
# The `NestedFlow` component is attached here.
|
|
setattr(self, "nested_flow", NestedFlow())
|
|
# Run the `NestedFlow` component.
|
|
getattr(self, "wonested_flowrk").run()
|
|
|
|
|
|
But it is usually more readable to use Lightning built-in :class:`~lightning_app.structures.Dict` or :class:`~lightning_app.structures.List` as follows:
|
|
|
|
.. code-block:: python
|
|
|
|
from lightning_app.structures import Dict
|
|
|
|
|
|
class RootFlow(L.LightningFlow):
|
|
def __init__(self):
|
|
super().__init__()
|
|
self.dict = Dict()
|
|
|
|
def run(self):
|
|
if "work" not in self.dict:
|
|
# The `Work` component is attached here.
|
|
self.dict["work"] = Work()
|
|
self.dict["work"].run()
|
|
|
|
if "nested_flow" not in self.dict:
|
|
# The `NestedFlow` component is attached here.
|
|
self.dict["nested_flow"] = NestedFlow()
|
|
self.dict["nested_flow"].run()
|