设计模式C++描述----19.命令(Command)模式

一. 举例说明

我们知道，在多线程程序中，多个用户都给系统发 Read 和 Write 命令。这里有几点需要说明：

1. 首先明确一点，所有的这些 Read 和 Write 命令都是调用一个库函数。

2. 用户并不需要知道别的用户的存在，也不管别人发不发命令，只管自己发命令，最后给结果即可。

3. 这些命令先是到了一个消息队列里面，然后由消息队列调用库函数。

结构图如下：

代码如下：

[cpp] class Command;

//实施与执行类
class Reciever
{
public:
    void Action()
    {
        cout<<"Do action !!"<<endl;
    }
};

//抽象命令类
class Command
{
public:
    virtual ~Command() {}

    virtual void Excute() = 0;

protected:
    Command() {}
};

//Read 命令
class Read_Command:public Command
{
public:
    Read_Command(Reciever* rev)
    {
        this->_rev = rev;
    }

    ~Read_Command()
    {
        delete this->_rev;
    }

    void Excute()
    {
        cout<<"Read Command..."<<endl;
        _rev->Action();
    }

private:
    Reciever* _rev;
};

//Write 命令
class Write_Command:public Command
{
public:
    Write_Command(Reciever* rev)
    {
        this->_rev = rev;
    }

    ~Write_Command()
    {
        delete this->_rev;
    }

    void Excute()
    {
        cout<<"Write_Command..."<<endl;
        _rev->Action();
    }

private:
    Reciever* _rev;
};

//要求命令执行的类
class Invoker
{
public:
    Invoker(Command* cmd)
    {
        _cmd = cmd;
    }

    Invoker()
    {
    }

    ~Invoker()
    {
        delete _cmd;
    }

    //通知执行类执行
    void Notify()
    {
        list<Command*>::iterator it = cmdList.begin();

        for (it; it != cmdList.end(); ++it)
        {
            _cmd = *it;
          _cmd->Excute();
        }
    }

    //添加命令
    void AddCmd(Command* pcmd)
    {
        cmdList.push_back(pcmd);
    }

    //删除命令
    void DelCmd(Command* pcmd)
    {
        cmdList.remove(pcmd);
    }

private:
    Command* _cmd;

    list<Command*> cmdList;
};

//测试代码 www.zzzyk.com
int main(int argc,char* argv[])
{
    Reciever* rev = new Reciever(); //定义一个执行类

    Command* cmd1 = new Read_Command(rev);//Read 命令
    Command* cmd2 = new Write_Command(rev);//Write 命令

    Invoker inv; //管理所有命令

    inv.AddCmd(cmd1);
    inv.AddCmd(cmd2);
    inv.Notify(); //通知执行类，执行

    inv.DelCmd(cmd1);
    inv.Notify();

    return 0;
}
class Command;

//实施与执行类
class Reciever
{
public:
void Action()
{
cout<<"Do action !!"<<endl;
}
};

//抽象命令类
class Command
{
public:
virtual ~Command() {}

virtual void Excute() = 0;

protected:
Command() {}
};

//Read 命令
class Read_Command:public Command
{
public:
Read_Command(Reciever* rev)
{
this->_rev = rev;
}

~Read_Command()
{
delete this->_rev;
}

void Excute()
{
cout<<"Read Command..."<<endl;
_rev->Action();
}

private:
Reciever* _rev;
};

//Write 命令
class Write_Command:public Command
{
public:
Write_Command(Reciever* rev)
{
  this->_rev = rev;
}

~Write_Command()
{
  delete this->_rev;
}

void Excute()
{
  cout<<"Write_Command..."<<endl;
  _rev->Action();
}

private:
Reciever* _rev;
};

//要求命令执行的类
class Invoker
{
public:
Invoker(Command* cmd)
{
_cmd = cmd;
}

Invoker()
{
}

~Invoker()
{
delete _cmd;
}

补充：软件开发 , C++ ,