Allow CreateVectorOfStrings() to work with any string-type. (#7238)

Any string type that is supported by CreateString(), e.g.
const char* or string_view will now also work.

Signed-off-by: Henner Zeller <hzeller@google.com>

include/flatbuffers/flatbuffer_builder.h

@@ -716,15 +716,18 @@ class FlatBufferBuilder {
     return CreateVector(elems);
   }
 
-  /// @brief Serialize a `std::vector<std::string>` into a FlatBuffer `vector`.
+  /// @brief Serialize a `std::vector<StringType>` into a FlatBuffer `vector`.
+  /// whereas StringType is any type that is accepted by the CreateString()
+  /// overloads.
   /// This is a convenience function for a common case.
   /// @param v A const reference to the `std::vector` to serialize into the
   /// buffer as a `vector`.
   /// @return Returns a typed `Offset` into the serialized data indicating
   /// where the vector is stored.
-  template<typename Alloc = std::allocator<std::string>>
+  template<typename StringType = std::string,
+           typename Alloc = std::allocator<std::string>>
   Offset<Vector<Offset<String>>> CreateVectorOfStrings(
-      const std::vector<std::string, Alloc> &v) {
+      const std::vector<StringType, Alloc> &v) {
     return CreateVectorOfStrings(v.cbegin(), v.cend());
   }
 

tests/test.cpp

@@ -136,6 +136,19 @@ flatbuffers::DetachedBuffer CreateFlatBufferTest(std::string &buffer) {
   names2.push_back("mary");
   auto vecofstrings2 = builder.CreateVectorOfStrings(names2);
 
+  // Creating vectors from types that are different from std::string
+  std::vector<const char *> names3;
+  names3.push_back("foo");
+  names3.push_back("bar");
+  builder.CreateVectorOfStrings(names3);  // Also an accepted type
+
+#ifdef FLATBUFFERS_HAS_STRING_VIEW
+  std::vector<flatbuffers::string_view> names4;
+  names3.push_back("baz");
+  names3.push_back("quux");
+  builder.CreateVectorOfStrings(names4);  // Also an accepted type
+#endif
+
   // Create many vectors of strings
   std::vector<std::string> manyNames;
   for (auto i = 0; i < 100; i++) { manyNames.push_back("john_doe"); }