基本概念

命令模式（Command），将一个请求封装为对象，从而使你看用不同的请求对客户端进行参数化；对请求排队或记录请求日志，以及支持可撤销操作。

命令模式的作用：

1. 能比较容易的设计一个命令队列；

2. 在需要的情况下，可以比较容易地将命令记入日志；

3. 允许接收请求的一方决定是否要否决请求；

4. 可以容易的实现对请求的撤销和重做；

5. 由于加进的新的具体命令类不影响其他类，因此增加新的具体命令类很容易。

UML图如下（此图来源于大话设计模式）

代码与实例

程序运行截图如下：

源码如下：

Head.h

#ifndef HEAD_H
#define HEAD_H#include <iostream>
#include <string>
using namespace std;//Receiver类，知道如何实施与执行一个与请求相关的操作，任何类都可能作文一个接收者
class Receiver{public:void action();~Receiver();
};//Command类，用来声明执行操作的接口
class Command{public:virtual void execute();Command(Receiver *receiver);virtual ~Command();protected:Command();Command(Command &c);Command &operator = (Command &c);Receiver *m_receiver;
};//ConcreteCommand类，将一个接收者对象绑定于一个动作，调用接收这相应的操作，以实现Execute
class ConcreteCommand: public Command{public:ConcreteCommand(Receiver *receiver);void execute();~ConcreteCommand();
};//Invoker类，要求该命令执行这个请求
class Invoker{public:void setCommand(Command *command);void executeCommand();private:Command *m_command;
};#endif

Head.cpp

#include "Head.h"void Command::execute()
{}Command::~Command()
{cout << "Command::~Command()" << endl;
}Command::Command()
{}Command::Command(Command &c)
{}Command::Command(Receiver *receiver)
{m_receiver = receiver;
}Command & Command::operator=(Command &c)
{return Command();
}void Receiver::action()
{cout << "执行请求！" << endl;
}Receiver::~Receiver()
{cout << "Receiver::~Receiver()" << endl;
}ConcreteCommand::ConcreteCommand(Receiver *receiver) : Command(receiver)
{}void ConcreteCommand::execute()
{m_receiver->action();
}ConcreteCommand::~ConcreteCommand()
{cout << "ConcreteCommand::~ConcreteCommand()" << endl;
}void Invoker::setCommand(Command *command)
{m_command = command;
}void Invoker::executeCommand()
{m_command->execute();
}

main.cpp

#include "Head.h"int main(int *argc, int *argv){Receiver *r = new Receiver;Command *c = new ConcreteCommand(r);Invoker *i = new Invoker;i->setCommand(c);i->executeCommand();delete r;delete c;delete i;getchar();return 0;
}