Is there an equivalent to "Any" type in protocol buffer?

[exhau]

A lot of buffers have been defined.

Now I wish to add a type to wrap them. For example, assign a time to each buffer.

table Message { time:long; contentType:string; content:Any; }

It is impossible to add all types to a Union.

One potential solution could be

table Message { time:long; contentType:string; content:[ubyte]; }

The problem is, how to build the message without copy/rebuild after the content(eg. monster) is ready?

Take your sample code as an example,

auto orc = CreateMonster(builder, &position, 150, 80, name, inventory, Color_Red, weapons, Equipment_Weapon, axe.Union());

auto content = builder.CreateVector(... ); // if we do this way, the monster buffer would be copied // it seems that i can manually use StartVector/EndVector(). Not sure there is any issue.

auto msg = CreateMessage(builder, 11111, content);

---

As for read, I think we may cast it by

auto enty = GetMessage(builder.GetBufferPointer()); auto buf = enty->content(); auto monster = GetMonster(buf->data());

Could you please hint what is the best practice to do this?

[aardappel]

Yes, unions are intended for this purpose.

You could indeed copy it, from another FlatBufferBuilder.

It is also possible to without copying, but there is no nice API for that at the moment. You would do:

fbb.Finish(CreateMyRootObject(..));

At this point, you have a complete FlatBuffer in the builder, but you can still prefix it.

auto size = fbb.GetSize();
fbb.StartVector(size, sizeof(uint8_t));
assert(size == fbb.GetSize());
auto vec = fbb.EndVector(size);

The StartVector won't do anything, since there is nothing to align. You can now finish the buffer a second time.

[exhau]

Thank you. The method that finishes flatbufferbuilder twice works .