c++/qt设计模式-命令模式

文章中部分内容和思路来自《Head First设计模式》

模式定义

将"请求"封装成对象，以便使用不同的请求、队列或日志来参数化其他对象。命令模式也支持可撤销的

模式类图

典型案例

1.案例说明假设客户去银行办理存取款业务，业务员根据客户业务的不同对客户账户进行存取款操作。在这个案例中，我们可以将业务员看做命令的发出者，客户账号看做命令接收者，具体命令是存款取款2.代码实现----------ICommond.h----------#ifndef ICOMMOND_H

#define ICOMMOND_H

class ICommond

{

public:

virtual void execute() = 0;

};

#endif // ICOMMOND_H

 ----------------MoneyInCommond.h----------------#ifndef MONEYINCOMMOND_H

#define MONEYINCOMMOND_H

#include "ICommond.h"

#include "Account.h"

class MoneyInCommond : public ICommond

{

public:

MoneyInCommond(Account *acc, float amount);

virtual ~MoneyInCommond();

public:

virtual void execute();

private:

Account *_acc;

float _amount;

};

#endif // MONEYINCOMMOND_H

 ------------------MoneyInCommond.cpp------------------#include "MoneyInCommond.h"

MoneyInCommond::MoneyInCommond(Account *acc, float amount)

{

_acc = acc;

_amount = amount;

}

MoneyInCommond::~MoneyInCommond()

{

}

void MoneyInCommond::execute()

{

_acc->moneyIn(_amount);

}

 -----------------MoneyOutCommond.h-----------------#ifndef MONEYOUTCOMMOND_H

#define MONEYOUTCOMMOND_H

#include "ICommond.h"

#include "Account.h"

class MoneyOutCommond : public ICommond

{

public:

MoneyOutCommond(Account *acc, float amount);

virtual ~MoneyOutCommond();

public:

virtual void execute();

private:

Account *_acc;

float _amount;

};

#endif // MONEYOUTCOMMOND_H

 -------------------MoneyOutCommond.cpp-------------------#include "MoneyOutCommond.h"

MoneyOutCommond::MoneyOutCommond(Account *acc, float amount)

{

_acc = acc;

_amount = amount;

}

MoneyOutCommond::~MoneyOutCommond()

{

}

void MoneyOutCommond::execute()

{

_acc->moneyOut(_amount);

}

 ---------Account.h---------#ifndef ACCOUNT_H

#define ACCOUNT_H

class Account

{

public:

Account();

public:

void moneyIn(float value); // 存钱

void moneyOut(float value); // 取钱

float getTotal() const; // 获取总额

private:

float _total;

};

#endif // ACCOUNT_H

 -----------Account.cpp-----------#include "Account.h"

Account::Account()

{

_total = 0;

}

void Account::moneyIn(float value)

{

_total += value;

}

void Account::moneyOut(float value)

{

_total -= value;

}

float Account::getTotal() const

{

return _total;

}

 ---------Invoker.h---------#ifndef INVOKER_H

#define INVOKER_H

#include "ICommond.h"

class Invoker

{

public:

Invoker();

public:

void setCommond(ICommond *cmd);

void commondExecute();

private:

ICommond *_cmd;

};

#endif // INVOKER_H

 -----------Invoker.cpp-----------#include "Invoker.h"

Invoker::Invoker()

{

}

void Invoker::setCommond(ICommond *cmd)

{

_cmd = cmd;

}

void Invoker::commondExecute()

{

_cmd->execute();

}

 --------main.cpp--------/**

* 设计模式-命令模式

* 要素：1,执行者 2,抽象命令 3,具体命令 4,接受者[作用对象]

*/

#include <QCoreApplication>

#include <QDebug>

#include "Account.h"

#include "Invoker.h"

#include "MoneyInCommond.h"

#include "MoneyOutCommond.h"

int main(int argc, char *argv[])

{

QCoreApplication a(argc, argv);

Account *acc = new Account;

MoneyInCommond *inCmd = new MoneyInCommond(acc, 34);

Invoker *bankAssist = new Invoker;

    bankAssist->setCommond(inCmd); // 银行职员先给账户存钱

bankAssist->commondExecute();

    qDebug() << "账户余额：" << acc->getTotal();

    MoneyOutCommond *outCmd = new MoneyOutCommond(acc, 45);

bankAssist->setCommond(outCmd); // 银行职员从账户取钱

bankAssist->commondExecute();

    qDebug() << "账户余额：" << acc->getTotal();

    delete outCmd;

outCmd = NULL;

    delete bankAssist;

bankAssist = NULL;

    delete inCmd;

inCmd = NULL;

    delete acc;

acc = NULL;

    return a.exec();

}

案例不太好，但基本能说明问题，《Head First》一书中举了一个遥控器的例子，有兴趣的可以看看