onMessage<M> method

void onMessage<M>(
  1. void build(
    1. MessageHandlerBuilder<M, D, void> b
    ), {
  2. M? message,
})

Describes how messages of type M should be handled by this state.

The build function is called with a MessageHandlerBuilder that can be used to describe the behavior of the message handler.

Implementation

void onMessage<M>(void Function(MessageHandlerBuilder<M, D, void> b) build, {M? message}) {
  var builder = MessageHandlerBuilder<M, D, void>(key, _makeVoidMessageContext, _log, null);
  build(builder);
  if (builder.descriptor != null) {
    var messageKey = message ?? M;
    _messageHandlerMap[messageKey] = builder.descriptor!;
  }
}