设计模式十八（观察者模式，python语言实现）

基本原理请参考相应书籍，这里直接给实例

观察者模式通过主题订阅的形式使得系统两个部分解耦。

基本说明本系统由两大部分组成：雷达（subject）和哨所（observer）

其中雷达分为： 空域雷达（RadarStationS） 和海域雷达（RadarStationB）

哨所分为：指挥本部（SentryO），一号哨所，二号哨所，三号哨所。



指挥本部订阅了这两种雷达信息

一号哨所、二号哨所 执行的是海域任务 ，订阅了海域雷达信息

三号哨所 执行的是空间任务 ，订阅了空间雷达信息

# -*- coding: GB18030 -*-
######################################################
# 
# Observer.py
# Python implementation of the Class Observer
# Generated by Enterprise Architect
# Created on:      15-十二??2012 8:30:17
# 
#######################################################

 

from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
from future_builtins import *
    

class Observer(object):
    """This class defines an updating interface for objects that should be notified of
    changes in a subject.
    """
    def __init__(self, name=None):
        self.name=name
        pass

    def Update(self, radar):
        str=self.name+'\n   收到情报：'+radar.GetState()+ " 情报来源："+radar.name +'\n   执行：'+self.work
        print(str)
       
        pass

 

class SentryA(Observer):
    """This class defines an updating interface for objects that should be notified of
    changes in a subject.
    """

    def __init__(self, name='一号哨所'):
        super(SentryA,self).__init__(name)
        self.work='海监船马上跟进，执行海巡'
        pass

class SentryB(Observer):
    """This class defines an updating interface for objects that should be notified of
    changes in a subject.
    """
    def __init__(self, name='二号哨所'):
        super(SentryB,self).__init__(name)
        self.work='护卫舰护航，进入戒备状态'        
        pass

class SentryC(Observer):
    """This class defines an updating interface for objects that should be notified of
    changes in a subject.
    """

    def __init__(self, name='三号哨所'):
        super(SentryC,self).__init__(name)
        self.work='马上执行空巡，进一步确定情况'          
        pass

class SentryO(Observer):
    """This class defines an updating interface for objects that should be notified of
    changes in a subject.
    """

    def __init__(self, name='指挥本部'):
        super(SentryO,self).__init__(name)
        self.work='按党中央统一部署执行任务'           
        pass

class Subject(object):
    """This class knows its observers and provides an interface for attaching and
    detaching Observer objects.
    """
    m_Observer= Observer()

    def __init__(self, name):
        """m_Observer= Observer()
        """
        self.name=name
        self.ls=list()
        self.state=None
        pass

    def Attach(self, observer):
        self.ls.append(observer)
        pass

    def Detach(self, obsever):
        if obsever in self.ls:
            self.ls.remove(observer)
        pass

    def GetState(self):
        return self.state
        pass

    def Notify(self):
       
        for observer in self.ls:
            observer.Update(self)
            pass
        
        pass

    def SetState(self, state):
        self.state=state
        pass
    
    
    
class RadarStationA(Subject):
    """This class stores the state of interest to ConcreteObserver objects and sends
    notification to its observers when its state changes.
    """
    def __init__(self, name='空域雷达'):
        super(RadarStationA,self).__init__(name)
        pass

class RadarStationB(Subject):
    """This class stores the state of interest to ConcreteObserver objects and sends
    notification to its observers when its state changes.
    """
    def __init__(self, name='海域雷达'):
        super(RadarStationB,self).__init__(name)        
        pass
    pass

 

#客户端
if(__name__=="__main__"):
    #观察者
    m_SentryA=SentryA()
    m_SentryB=SentryB()
    m_SentryC=SentryC()
    m_SentryO=SentryO()    
    
    #主题（监控雷达）
    m_RadarStationA=RadarStationA()
    m_RadarStationB=RadarStationB()   
    
    #订阅主题A（空间监控雷达）
    m_RadarStationA.Attach(m_SentryO)    
    m_RadarStationA.Attach(m_SentryC)  
    #订阅主题B（海域监控雷达）
    m_RadarStationB.Attach(m_SentryO)        
    m_RadarStationB.Attach(m_SentryA)
    m_RadarStationB.Attach(m_SentryB) 
    
    #主题A监控到信息，并通知订阅??
    m_RadarStationA.SetState('我领空发现不明飞行物')
    m_RadarStationA.Notify() 
    
    print('\n')
    #主题B监控到信息，并通知订阅??   
    m_RadarStationB.SetState('我海域发现不明船船只')
    m_RadarStationB.Notify()

#运行结果：