AdvancedUsage

Extension

Assume you have a proto file:

message Test1 {
  extensions 10 to max;
}
message Test2 {
  extend Test1 {
    optional Test2 foo_bar = 10;
  }
}

Then you can use [] operator to set extension fields:

var test1:Test1 = new Test1();
test1[Test2.FOO_BAR] = new Test2();
test1.writeTo(output);

Note: Before you deserialize a message which has extension data, you must touch the class which defines the extension field, or the extension data will be treated as unknown fields. For example:

void(Test2.FOO_BAR); // Touch Test2 to static initialize it.
var test1:Test1 = new Test1();
test1.mergeFrom(input);
var test2:Test2 = test1[Test2.FOO_BAR];

Another way to initialize extension fields is including initializer.as.inc, which is in the output directory specified by as3_out of your protoc command.

include "initializer.as.inc"

Bindable

You can use (as3_bindable) option to generate classes with [Bindable] metadata tag. Just like this:

import "options.proto"
message MyBindable {
  option (as3_bindable) = true;
}

AMF Wrapper

The Protocol Buffer wire format is not self-delimiting, so you may use another wrapper packet format to store the message type and length. A simple way is wrapping Protocol Buffer messages into AMF stream. There are two options designed for wrapping Protobuf messages in AMF stream: (as3_amf_auto_alias) and (as3_amf_alias).

import "options.proto"
message MyAMF {
  option (as3_amf_auto_alias) = true;
}
message MyAMF2 {
  option (as3_amf_alias) = "com.sample.MyAMFWithCustomAliasName";
}

Both the two options add [RemoteClass] metadata tag to the messages. Now you can invoke IDataInput.readObject() and IDataOutput.writeObject() with these messages in Flex applications.