post<M> method

void post<M>({
  1. M getMessage(
    1. TransitionContext ctx
    )?,
  2. M? message,
  3. String? label,
})

Posts a message to be processed by the state machine when a transition occurs.

If getMessage is provided, the function will be evaluated when the transition occurs, and the returned message will be posted. Otherwise a message must be provided.

var state1 = StateKey('s1');
var builder = StateTreeBuilder(initialState: state1);

builder.state(state1, (b) {
  // Post a MyMessage message when this state is entered.
  b.onEnter((b) => b.post(getMessage: (transCtx) => MyMessage()));
});

This action can be labeled when formatting a state tree by providing a label.

Implementation

void post<M>({
  M Function(TransitionContext ctx)? getMessage,
  M? message,
  String? label,
}) {
  if (getMessage == null && message == null) {
    throw ArgumentError('getMessage or message must be provided');
  } else if (getMessage != null && message != null) {
    throw ArgumentError('One of getMessage or message must be provided');
  }
  var _getMessage = getMessage ?? (_) => message!;
  _handler = _TransitionHandlerDescriptor.post<M>(_getMessage, label);
}