面向对象系统分析与设计_观察者模式.ppt

1、2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,1,OO System Analysis /取得温度 float humidity = getHumidity(); /取得湿度 float pressure = getPressure(); /取得气压 currentConditionsDisplay.update(temp, humidity, pressure); /同步显示当前天气状况 statisticsDisplay.update(temp, humidity, pressure

2、); /同步显示天气统计信息 forecastDisplay.update(temp, humidity, pressure); /同步显示天气预报信息 ,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,6,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,7,Our job is:,To create an app that uses the WheatherData object t

3、o update three displays.,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,8,The kernel of the problem,WeatherData object,to update if you require,displays,publishers,subscribers,to deliver if you subscribe,subject object,observer objects,to notify if you observe,2020年10月3

4、1日星期六,Neusoft Computer Science and Technology Department copy right,9,The Observer Pattern,The Observer Pattern defines a one-to-many relationship between objects so that when one object changes state, all of its dependents are notified and updated automatically.,2020年10月31日星期六,Neusoft Computer Scie

5、nce and Technology Department copy right,10,Class diagram for Observer Pattern,Each subject can have many observers,update() will be called when the Subjects state changes.,These methods will be called When to register as observers , remove themselves from Being observers, or update all the observer

6、s whenever state changes.,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,11,To develop app from the interface,Subject（被观察的对象接口） 规定ConcreteSubject的统一接口； 每个Subject可以有多个Observer； ConcreteSubject（具体被观察对象） 维护对所有具体观察者的引用的列表； 状态发生变化时会发送通知给所有注册的观察者。 Observer（观察者接口） 规定ConcreteOb

7、server的统一接口； 定义了一个update()方法，在被观察对象状态改变时会被调用。 ConcreteObserver（具体观察者） 维护一个对ConcreteSubject的引用； 特定状态与ConcreteSubject同步； 实现Observer接口，通过update()方法接收ConcreteSubject的通知。,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,12,顺序图,2020年10月31日星期六,Neusoft Computer Science and Techno

8、logy Department copy right,13,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,14,Designing the Weather Station,Exercise: A Spring Tour plan,Spring tour plan manage system need to maintain a collection of the participants Notify all members of the information about the plan Each member have their own arrival at the point of collection,2020年10月31日星期六,Neusoft Computer Science and Technology Department copy right,15,2020年10月31日星期六,Neusoft Computer