eventable 1.0.0

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 custom events. To make a custom event simply extend off of the Event class and specify an interface implementation, but you do not have to implement it as Event is in fact a Json_Object. One final note to be aware of is that events are emitted asynchronously. Usage is best described with a simple example:

##Example

class Dog extends Object with EventEmitter{

  static const String BARK = 'dog_bark';

  void bark(int volume){
    emitEvent(
        BARK,
        new BarkEvent()
        ..volume = volume);
  }
  
}

class Cat extends Object with EventDetector{

  void dogBarkHandler(BarkEvent event){
    if(event.volume > 10){
      runaway();
    }else{
      print('cat not disturbed');
    }
  }

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

}

class BarkEvent extends Event implements IBarkEvent{}
abstract class IBarkEvent{
  int volume;
}

void main(){

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

  cat.listen(dog, Dog.BARK, cat.dogBarkHandler);

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

}

##OMNI

There is a special event type called OMNI which is a top level string constant in the eventable library which has the value 'omni', this is a special value which allows you to listen to every event emitted by an EventEmitter with a single EventAction, therefore it is strongly recommended when implementing your own event types you do not use 'omni' or you may find incorrect program behaviour as a result of doing so.

##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 type from a specific EventEmitter once, therefore it is an error to try to attach more EventActions to the same EventEmitter/event type combination. If a second attempt is made by an EventDetector to listen to the same EventEmitter/event 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 *EventAction**s from that same event, if such an attempt is made a EmitTimeQueueChangeError will be thrown.