author = 'Administrator'

/usr/env/bin python
'''
  this is document
'''
class Event(object):
    '''
      事件初始化的一個方式
    '''
    def init(self,event_type,data=None):
        self._type = event_type
        self._data = data

@property
def type(self):
    return self._type

@property
def data(self):
    return self._data


class EventDispatcher(object):
     """
    event分發類 監聽和分發event事件
    """
     def init(self):

     #初始化事件
     self._events = dict()

 def __del__(self):
     self._events = None

 def has_listener(self,event_type,listener):
    if event_type in self._events.keys():
        return listener in self._events[event_type]
    else:
        return False

 def dispatch_event(self,event):
      """
    Dispatch an instance of Event class
    """
    # 分發event到所有關聯的listener
      if event.type in self._events.keys():
          listeners = self._events[event.type]

          for listener in listeners:
              listener(event)

 def add_event_listener(self,event_type,listener):
     #給某種事件類型添加listner
     if not self.has_listener(event_type,listener):
         listeners = self._events.get(event_type,[])
         listeners.append(listener)
         self._events[event_type] = listeners

 def remove_event_listener(self,event_type,listener):
     if self.has_listener(event_type,listener):
         listeners = self._events[event_type]
         if len(listeners) == 1:
             del self._events[event_type]
         else:
             listeners.remove(listener)
             self._events[event_type] = listeners


class MyEvent(Event):
    ASK = "askMyEvent"
    RESPOND = "respondMyEvent"
class WhoAsk(object):
    def init(self,event_dispatcher):
        self.event_dispatcher = event_dispatcher
        self.event_dispatcher.add_event_listener(
            MyEvent.RESPOND,self.on_answer_event
        )
    def ask(self):
        print("who are listener to me?")
        self.event_dispatcher.dispatch_event(MyEvent(MyEvent.ASK,self))

def on_answer_event(self,event):
    print("receive event %s",event.data)


class WhoRespond(object):
   def init(self,event_dispatcher):
       self.event_dispatcher = event_dispatcher
       self.event_dispatcher.add_event_listener(MyEvent.ASK,self.on_ask_event)
def on_ask_event(self,event):
       self.event_dispatcher.dispatch_event(MyEvent(MyEvent.RESPOND,self))
dispatcher = EventDispatcher()
who_ask = WhoAsk( dispatcher )
who_responde1 = WhoRespond( dispatcher )
who_responde2 = WhoRespond( dispatcher )
WhoAsk ask
who_ask.ask()</pre> 


 使用事件驅動的方式寫代碼也不是一天兩天了，今天突然發現這玩意居然有個理論在支撐這個。瞬間感到自己學的都是一點點皮毛而己。 
 
 python的事件模型的優勢是，可以直接將某個方法放入事件中，這個好象要比java先進一點。