设计模式C++描述----19.命令(Command)模式 (一)

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 !!"< }
};

//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..."< _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..."< _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::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 cmdList;
};


//测试代码 www.2cto.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 !!"< }
};

//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..."< _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..."< _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::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 cmdList;
};

//测试代码
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)