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php中的设计模式之门面模式

Jun 23, 2016 pm 01:39 PM

<?php /**   (1)外观模式(Facade)也叫门面模式,为子系统中的一组接口提供一个一致的界面,此模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。     为一些复杂的子系统提供一组接口 (2)主要角色门面(Facade)角色?	此角色将被客户端调用?	知道哪些子系统负责处理请求?	将用户的请求指派给适当的子系统子系统(subsystem)角色?	实现子系统的功能?	处理由Facade对象指派的任务?	没有Facade的相关信息,可以被客户端直接调用?	可以同时有一个或多个子系统,每个子系统都不是一个单独的类,而一个类的集合。每个子系统都可以被客户端直接调用,或者被门面角色调(3)使用情况 :	首先,在设计初期阶段,应该要有意识将不同的两个层分离,比如经典的三层架构,就需要考虑在数据访问层和业务逻辑层、业务逻辑层和表示层的层与层之间建立外观Facade,这样可以为复杂的子系统提供一个简单的接口,使得耦合度大大降低。	其次,在开发阶段,子系统往往因为不断的重构演化而变得越来越复杂,大多数的模式使用时也都会产生很多很小的类,这本是好事,但也给外部调用它们的用户程序带来了使用上的困难,增加外观Facade可以提供一个简单的接口,减少它们之间的依赖。	第三,在维护一个遗留的大型系统时,可能这个系统已经非常难以维护和扩展了,但因为它包含非常重要的功能,新的需求开发必须要依赖于它。此时,用外观模式Facade也是非常合适的。你可以为新系统开发一个外观Facade类,来提供设计粗糙或高度复杂的遗留代码的比较清晰的简单接口,让新系统与Facade对象交互,Facade与遗留代码交互所有复杂的工作。”(4) 具体事例 比如我关机,整个过程包括关闭显示器,关闭pc机器,关闭电源 ,关机的按钮就是门面的角色,其他为子系统*/// 门面抽象接口 interface Facade{	    public function turnOn() ;    public function turnOff() ;}// (1) 关闭显示器class PcLight {    public function turnOn() {}    public function turnOff() {		echo 'turn off PcLight <br>' ;	}   }//(2) pc 机器class Pcmachine {    public function turnOn() {}     public function turnOff() {		echo 'turn off PcMathion <br>' ;	}}// (3) 关闭电源class Power {    public function turnOn() {}     public function turnOff() {		echo 'turn off Power <br>' ; 	}}// 关机的门面角色 class PcFacade implements Facade{		private  $PcLight ; 	private  $Pcmachine ; 	private  $Power ;  	public function __construct(){	 $this->PcLight = new PcLight();         $this->Pcmachine = new Pcmachine();         $this->Power = new Power();	}		// 门面角色的应用	 public function turnOff() {           $this->PcLight ->turnOff();          $this->Pcmachine ->turnOff();          $this->Power ->turnOff();	 }         public function turnOn() {}	}// 应用$button = new PcFacade(); $button ->turnOff(); /* 其实门面模式就是把几个子系统(实例或者类.统一一个统一的接口进行执行,客户端不用关注子系统,只用门面即可 )
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