eventable 5.1.1

simple event system for implementing model->event->view design pattern.

#Eventable

Eventable provides 2 mixins to make your classes eventable, EventEmitter and EventDetector. Simply use these mixins to make your types either emit, detect or do both for asynchronous events. An Event can carry any data object, to listen for an Event carrying a particular data type just listen for that data type. Usage is best described with a simple example:

##Example

class Dog extends Object with EventEmitter{

  void bark(int volume){
    emitEvent(new Bark(volume));
  }
  
}

class Cat extends Object with EventDetector{

  void dogBarkHandler(Event<Bark> event){
    var bark = event.data;
    if(bark.volume > 10){
      runaway();
    }else{
      print('cat not disturbed');
    }
  }

  void runaway(){
    print('cat running away');
  }

}

class Bark{
  final int volume;
  Bark(this.volume);
}

void main(){

  var dog = new Dog();
  var cat = new Cat();

  cat.listen(dog, Bark, cat.dogBarkHandler);

  dog.bark(9);  // cat not disturbed
  dog.bark(11); // cat runs away

}

##Omni

There is a special event data type Omni which allows detectors to listen to every event emitted by an EventEmitter with a single EventAction.

##EventAction

A typedef is specified in the eventable library which serves as the function signature accepted as the last argument to an EventDetectors listen method. The signature is:

typedef void EventAction(Event event);

##DuplicateEventSettingError

A given EventDetector can only listen to a specific event-data-type from a specific EventEmitter once, therefore it is an error to try to attach more EventActions to the same EventEmitter / event-data-type combination. If a second attempt is made by an EventDetector to listen to the same EventEmitter / event-data-type combination a DuplicateEventSettingError will be thrown.

##EmitTimeQueueChangeError

It is not permitted to add or remove EventActions whilst the event is being emitted, meaning you may not attach an EventAction to an event which adds or removes EventActions from that same event-data-type queue, if such an attempt is made a EmitTimeQueueChangeError will be thrown. to remove EventActions for an emitting Event it is best to do so in the finished Future property on the Event object.