行为模式之命令模式(Command Pattern)C++实现

命令模式(Command Pattern)行为模式.

命令模式将“请求”封装成对象，以便使用不同的请求、队列或者日志来参数化其他对象。命令模式也支持可撤销的操作。

命令模式可以用在队列请求和日志请求。

餐厅对象对应到命令模式包括：command(订单)，execute()(orderUP()),Client(顾客),Invoker(女招待),Receiver(快餐厨师),setCommand()(takeOrder())

命令模式的类图如下：

Client创建一个ConcreteCommand，并设置接收者。

Receiver接收者知道如何进行必要的工作，实现这个请求。任何类都可以当接收者。

Invoker这个调用者持有一个命令对象，并在某个时间点调用命令对象的execute()方法，将请求付诸实行。

Command为所有的命令声明了一个接口，调用命令对象的execute()方法，就可以让接收者进行相关的动作。

遥控器的类图：

RemoteLoader相当于主调函数。RemoteControl相当于遥控器，用setCommand()装载命令，用onButtonWasPushed()来控制遥控器。LightOnCommand对象继承Command接口并持有一个接收者对象(如Light)。

流程如下：1.创建一个遥控器RemoteControl，即调用者对象Invoker。

2.创建接收者Light,即Receiver
3. 遥控器RemoteControl调用setCommand()装载命令。

4. RemoteControl控制命令

将请求封装在一个对象(command)中,并将请求的接受者放到具体的command中 (LightOnCommand)Receiver，从而实现调用操作的对象和操作的具体实现者之间的解耦。

HeadFirst 遥控器的例子实现C++

Receiver.h 头文件：

#ifndef _RECEIVER_H_#define _RECEIVER_H_//Reciever.h//命令接收者class Light{ public:Light();~Light();void on();void off();};class Stereo{public: Stereo();~Stereo();void on();void setCD();void setVolume(int volume);void off();};#endif
Receiver.CPP

#include"Receiver.h"#include<iostream>using namespace std;Light::Light(){}Light::~Light(){}void Light::on(){cout<<"light is on...."<<endl;}void Light::off(){cout<<"light is off..."<<endl;}Stereo::Stereo(){}Stereo::~Stereo(){}void Stereo::on(){cout<<"stereo is on ..."<<endl;}void Stereo::setCD(){cout<<"stereo is set for CD input"<<endl;}void Stereo::setVolume(int volume){cout<<"stereo volume set to "<<volume<<endl;}void Stereo::off(){cout<<"stereo is off..."<<endl;}
Command.h头文件

#ifndef _COMMAND_H_#define _COMMAND_H_class Light;class Stereo;//命令接口class Command{public:virtual ~Command();virtual void Execute()=0;protected:Command();private:};//空命令class NoCommand:public Command{public:NoCommand();~NoCommand();void Execute();protected:private:};//具体的命令class LightOnCommand:public Command{public:LightOnCommand(Light* pRec);~LightOnCommand();void Execute();protected:private:Light* pRec; //命令的接收者};class LightOffCommand:public Command{public:LightOffCommand(Light *pRec);~LightOffCommand();void Execute();protected:private:Light * pRec;//命令的接收者};class StereoOnWithCDCommand:public Command{public:StereoOnWithCDCommand(Stereo * pRec);~StereoOnWithCDCommand();void Execute();protected:private:Stereo * pRec;};class StereoOffWithCDCommand:public Command{public:StereoOffWithCDCommand(Stereo * pRec);~StereoOffWithCDCommand();void Execute();protected:private:Stereo * pRec;};#endif
Command.CPP源文件

#include "Command.h"#include"Receiver.h"Command::Command(){}Command::~Command(){}NoCommand::NoCommand(){}NoCommand::~NoCommand(){}void NoCommand::Execute(){ }LightOnCommand::LightOnCommand(Light *pRec){this->pRec=pRec;}LightOnCommand::~LightOnCommand(){}void LightOnCommand::Execute(){ pRec->on();}LightOffCommand::LightOffCommand(Light *pRec){this->pRec=pRec;}LightOffCommand::~LightOffCommand(){}void LightOffCommand::Execute(){ pRec->off();}StereoOnWithCDCommand::StereoOnWithCDCommand(Stereo *pRec){this->pRec=pRec;}StereoOnWithCDCommand::~StereoOnWithCDCommand(){}void StereoOnWithCDCommand::Execute(){pRec->on();pRec->setCD();pRec->setVolume(11);}StereoOffWithCDCommand::StereoOffWithCDCommand(Stereo *pRec){this->pRec=pRec;}StereoOffWithCDCommand::~StereoOffWithCDCommand(){}void StereoOffWithCDCommand::Execute(){this->pRec->off();}
Invoker.h头文件

#ifndef _INVOKER_H_#define _INVOKER_H_#include<list>#include<vector>using namespace std;class Command;//请求发送者class RemoteControl{public:RemoteControl(); ~RemoteControl(); void setCommand(int slot,Command *pOnCmd,Command *pOffCmd);void onButtonWasPushed(int slot);void offButtonWasPushed(int slot);protected:private://list<Command *>* pOnCmd;//list<Command *>* pOffCmd;vector<Command *> pOnCmd;vector<Command *> pOffCmd;};#endif
Invoker.CPP

#include "Invoker.h"#include "Command.h"RemoteControl::RemoteControl(){Command *pCmd=new NoCommand();for(int i=0;i<2;i++){ pOnCmd.push_back(pCmd); pOffCmd.push_back(pCmd);//pOnCmd->push_front(pCmd);//pOffCmd->push_front(pCmd);}}RemoteControl::~RemoteControl(){}void RemoteControl::setCommand(int slot, Command *pOnCmd, Command *pOffCmd){ this->pOnCmd.at(slot)=pOnCmd;this->pOffCmd.at(slot)=pOffCmd;}void RemoteControl::onButtonWasPushed(int slot){this->pOnCmd.at(slot)->Execute();}void RemoteControl::offButtonWasPushed(int slot){this->pOffCmd.at(slot)->Execute();}
主函数main.CPP

#include"Command.h"#include"Receiver.h"#include"Invoker.h"#include <iostream>using namespace std;int main(int argc,char* argv[]){ RemoteControl *remoteControl=new RemoteControl();//创建遥控器 //创建接收者Light *roomLight=new Light();Stereo *stereo=new Stereo();//创建命令LightOnCommand *roomLightOn=new LightOnCommand(roomLight);LightOffCommand *roomLightOff=new LightOffCommand(roomLight);StereoOnWithCDCommand *stereoOn=new StereoOnWithCDCommand(stereo); StereoOffWithCDCommand *stereoOff=new StereoOffWithCDCommand(stereo); //装载命令 remoteControl->setCommand(0,roomLightOn,roomLightOff); remoteControl->setCommand(1,stereoOn,stereoOff); //控制遥控器 remoteControl->onButtonWasPushed(0); remoteControl->onButtonWasPushed(1); remoteControl->offButtonWasPushed(0); remoteControl->offButtonWasPushed(1);return 0;}