軟件領域中的設計模式的重要性不言而喻。設計模式中運用了面向對象編程語言的重要特性:封裝、繼承、多態。雖然知道這些特性的定義但是並沒有做到真正的理解,這樣特性有什麼作用?用於什麼場合中等等問題,帶着疑問開始學習設計模式,主要參考《大話設計模式》和《設計模式:可複用面向對象軟件的基礎》兩本書。
命令模式(Command):將一個請求封裝爲一個對象,從而使你可用不同的請求對客戶進行參數化;對請求隊列或記錄請求日誌,以及支持可撤銷的操作;
特點:一、建立命令隊列;二、可以將命令記入日誌;三、接收請求的一方可以拒絕;四、添加一個新命令類不影響其它類;
命令模式把請求一個操作的對象與知道怎麼操行一個操作的對象分開;
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Receiver
{
public:
virtual void Action()
{
cout << "接收命令" << endl;
}
};
class Command
{
public:
Receiver* m_rece;
Command(Receiver* m_temp)
{
m_rece = m_temp;
}
virtual void Excute() = 0;
};
class ConcreteCommand :public Command
{
public:
ConcreteCommand(Receiver* m_p) :Command(m_p){}
virtual void Excute()
{
m_rece->Action();
}
};
class Invoker
{
private:
Command* m_Com;
public:
void SetCommand(Command* m_temp)
{
m_Com = m_temp;
}
void Notify()
{
m_Com->Excute();
}
};
int main()
{
Receiver* T = new Receiver();
Command* C = new ConcreteCommand(T);
Invoker* m_In = new Invoker();
m_In->SetCommand(C);
m_In->Notify();
return 0;
}
例:
#include <iostream>
#include <string>
#include <vector>
using namespace std;
//烤肉師傅
class Barbucer
{
public:
void MakeMutton()
{
cout << "烤羊肉" << endl;
}
void MakeChickenWing()
{
cout << "烤雞翅膀" << endl;
}
};
//抽象命令類
class Command
{
protected:
Barbucer* receiver;
public:
Command(Barbucer* temp)
{
receiver = temp;
}
virtual void ExecuteCmd() = 0;
virtual string show() = 0;
};
//烤羊肉命令
class BakeMuttonCmd : public Command
{
private:
string name = "烤羊排";
public:
BakeMuttonCmd(Barbucer* temp) : Command(temp){}
virtual void ExecuteCmd()
{
receiver->MakeMutton();
}
virtual string show()
{
return name;
}
};
//烤雞翅
class ChickenWingCmd : public Command
{
private:
string name = "烤雞翅";
public:
ChickenWingCmd(Barbucer* temp) : Command(temp){}
virtual void ExecuteCmd()
{
receiver->MakeChickenWing();
}
virtual string show()
{
return name;
}
};
//服務員類
class Waiter
{
protected:
vector<Command*> m_commandList;
public:
void SetCmd(Command* temp)
{
m_commandList.push_back(temp);
cout << "增加訂單 " << temp->show()<< endl;
}
//通知執行
void Notify()
{
cout << "客戶的菜單日誌如下:" << endl;
for (Command* p : m_commandList)
{
p->ExecuteCmd();
}
}
};
//客戶端
int main()
{
//店裏添加烤肉師傅、菜單、服務員等顧客
Barbucer* barbucer = new Barbucer();
Command* cmd = new BakeMuttonCmd(barbucer);
Command* cmd2 = new ChickenWingCmd(barbucer);
Waiter* girl = new Waiter();
//點菜
girl->SetCmd(cmd);
girl->SetCmd(cmd2);
//服務員通知
girl->Notify();
return 0;
}