设计模式 - 策略、命令(3)

 

1. 策略(Strategy)

   购物时的付款方式：可采用现金也可用信用卡

   策略模式：定义一系列算法，将各个算法封装起来，使算法可以相互替换。使算法独立于客户而变化。

   方法：利用OO的多态性，动态绑定的特点

   付款策略的实现：

using System;//抽象的付款策略abstract class PayMethod{ abstract public void Pay();}//具体的付款策略 - 现金支付class PayByCash : PayMethod{ public override void Pay() { Console.WriteLine("Pay by cash!"); }}//具体的付款策略 - 信用卡支付class PayByCreditCard : PayMethod{ public override void Pay() { Console.WriteLine("Pay by credit card!"); }}//对策略进行设置和调用的上下文class Context{ private PayMethod paymethod; //设置付款策略 public void SetPayMethod(PayMethod paymethod) { this.paymethod = paymethod; } //调用付款策略 public void Pay() { paymethod.Pay(); }}//策略模式的应用public class Client{ public static void Main(string[] args) { Context context = new Context(); context.SetPayMethod(new PayByCreditCard()); context.Pay(); //context.SetPayMethod(new PayByCash()); //此处体现了策略模式中，各策略的可替换性 //context.Pay(); Console.Read(); }}

 

2. 命令(Command)

   命令模式：将请求封装成对象。。。。。

   角色：抽象命令类，具体命令类，客户端，命令调用者，命令的接收者。

   实例(总开关统一给电灯和风扇发出开或关的命令)：

using System;//命令的接收者：风扇class Fan{ public void startRotate() { System.Console.WriteLine("Fan is rotating"); } public void stopRotate() { System.Console.WriteLine("Fan is not rotating"); }}//命令的接收者：电灯class Light{ public void turnOn() { System.Console.WriteLine("Light is on "); } public void turnOff() { System.Console.WriteLine("Light is off"); }}//命令的调用者：总开关class Switch{ private Command UpCommand, DownCommand; public Switch(Command Up, Command Down) { UpCommand = Up; // concrete Command registers itself with the invoker DownCommand = Down; } public void flipUp() { // invoker calls back concrete Command, which executes the Command on the receiver UpCommand.execute(); } public void flipDown() { DownCommand.execute(); }}//具体命令：抽象的命令public interface Command{ void execute();}//具体命令：开灯命令class LightOnCommand : Command{ private Light myLight; public LightOnCommand(Light L) { myLight = L; } public void execute() { myLight.turnOn(); }}//具体命令：关灯命令class LightOffCommand : Command{ private Light myLight; public LightOffCommand(Light L) { myLight = L; } public void execute() { myLight.turnOff(); }}//具体命令：开风扇命令class FanOnCommand : Command{ private Fan myFan; public FanOnCommand(Fan F) { myFan = F; } public void execute() { myFan.startRotate(); }}//具体命令：关风扇命令class FanOffCommand : Command{ private Fan myFan; public FanOffCommand(Fan F) { myFan = F; } public void execute() { myFan.stopRotate(); }}//客户端class CommandClient{ static void Main(string[] args) { Light testLight = new Light();//创建命令的接收者 - 电灯 //创建用于电灯的各种具体命令 LightOnCommand testLOC = new LightOnCommand(testLight); LightOffCommand testLFC = new LightOffCommand(testLight); Switch testSwitch = new Switch(testLOC, testLFC);//创建命令的调用者 - 总开关 testSwitch.flipUp(); testSwitch.flipDown(); Fan testFan = new Fan();//创建命令的接收者 - 风扇 //创建用于风扇的各种具体命令 FanOnCommand foc = new FanOnCommand(testFan); FanOffCommand ffc = new FanOffCommand(testFan); Switch ts = new Switch(foc, ffc);//创建命令的调用者 - 总开关 ts.flipUp(); ts.flipDown(); }}