Dart event mixin

events.dart

abstract class Events {
  Map _events;
  
  on(String events, Function callback, [Map datas]) {
    _events == null ? (_events = {}) : null;
    
    var eventsList = _splitEvents(events);
    for (int i = 0; i < eventsList.length; i++) {
      String event = eventsList[i];
      _events[event] == null ? (_events[event] = []): null;
      _events[event].add([callback, datas]);
    }
  }
  
  off(String events, [Function callback]) {
    _events == null ? (_events = {}) : null;
    
    var eventsList = _splitEvents(events);
    for (var i = 0; i < eventsList.length; i++) {
      String event = eventsList[i];
      
      if (_events[event] == null) {
        // Event not registered: nothing to do
        continue;
      
      } else if (callback == null) {
        // Callback not specified: delete full event
        _events[event].clear();
      
      } else {
        // Delete only event with specified callback
        List newHandlers = [];
        for (var j = 0; j < _events[event].length; j++) {
          var handler = _events[event][j];
          if (handler[0] != callback) {
            newHandlers.add(handler);
          }
        }
        _events[event] = newHandlers;
      }
    }
  }
  
  fire(String event, [Map args]) {
    if (_events == null || _events[event] == null) {
      return;
    }
    
    for (var i = 0; i < _events[event].length; i++) {
      var handler = _events[event][i];
      handler[0](args, handler[1]);
    }
  }
  
  List<String> _splitEvents(String events) {
    var spaces = new RegExp(r'\s+');
    List<String> splitteds = events.replaceAll(spaces, ' ')
                                   .trim()
                                   .split(' ');
    List<String> formattedEvents = [];
    for (int i = 0; i < splitteds.length; i++) {
      if (! formattedEvents.contains(splitteds[i])) {
        formattedEvents.add(splitteds[i]);
      }
    }
    
    return formattedEvents;
  }
}

Usage example

class Foo extends Object with Events {
    bar (Map args, Map datas) {
        print(args);
        print(datas);
    }
}

Foo foo = new Foo();

// Registering event
foo.on('launchbar other event', foo.bar, {'data1': 'bar1', 'data2': 'bar2'});

// Disable previous registered events
foo.off('other', foo.bar);
foo.off('event');

// Launch specified event with followed arguments
foo.fire('launchbar', {'arg1': 'value1', 'arg2': 'value2'});