第16章 行为型模式—命令模式

//行为型模式：命令模式
//场景：打飞机游戏
//角色控制器（如玩家）的主要操作：用导弹攻击、炸弹攻击来打飞机以及4个方向移动

#include <iostream>
#include <string>
#include <vector>

using namespace std;
//***********************************************抽象命令接口***********************************
//Command
class FighterCommand
{
public:
    virtual void execute() = 0;
};

//*************************************************接收者**************************************
//Receiver
class Fighter
{
public:
    void missile()
    {
        cout << "用导弹攻击！" << endl;
    }

    void bomb()
    {
        cout << "用炸弹攻击！" << endl;
    }

    void move (int direction)
    {
        switch(direction)
        {
        case 1:
            cout << "向上移动！" << endl;
            break;
        case 2:
            cout << "向下移动！" <<endl;
            break;
        case 3:
            cout << "向左移动！" << endl;
            break;
        case 4:
            cout << "向右移动！" <<endl;
            break;
        default:
            cout << "不移动！" << endl;
        }
    }
};

//*************************************ConcreteCommand***************************************
//导弹攻击命令
class MissileCommand : public FighterCommand
{
private:
    Fighter* fighter;
public:
    MissileCommand(Fighter* fighter)
    {
        this->fighter = fighter;
    }

    void execute()
    {
        fighter->missile();
    }
};

//炸弹攻击命令
class BombCommand : public FighterCommand
{
private:
    Fighter* fighter;
public:
    BombCommand(Fighter* fighter)
    {
        this->fighter = fighter;
    }

    void execute()
    {
        fighter->bomb();
    }
};

//移动命令
class MoveCommand : public FighterCommand
{
private:
    Fighter* fighter;
    int direction;
public:
    MoveCommand(Fighter* fighter, int direction)
    {
        this->fighter = fighter;
        this->direction = direction;
    }

    void execute()
    {
        fighter->move(direction);
    }
};

//***********************************************Invoker***********************************
//请求者
class Controller
{
private:
    FighterCommand* cmdMissible;
    FighterCommand* cmdBomb;
    FighterCommand* cmdMoveLeft;
    FighterCommand* cmdMoveRight;
public:
    Controller(FighterCommand* missible, FighterCommand* bomb,
               FighterCommand* left,     FighterCommand* right)
    {
        cmdMissible  = missible;
        cmdBomb      = bomb;
        cmdMoveLeft  = left;
        cmdMoveRight = right;
    }

    void missible()
    {
        cmdMissible->execute();
    }

    void bomb()
    {
        cmdBomb->execute();
    }

    void moveLeft()
    {
        cmdMoveLeft->execute();
    }

    void moveRight()
    {
        cmdMoveRight->execute();
    }
};

int main()
{
    Fighter fighter; //战士（命令接收者）

    //命令对象
    FighterCommand* cmdMissible  = new MissileCommand(&fighter);
    FighterCommand* cmdBomb      = new BombCommand(&fighter);
    FighterCommand* cmdMoveLeft  = new MoveCommand(&fighter, 3);
    FighterCommand* cmdMoveRight = new MoveCommand(&fighter, 4);

    //玩家（命令发出者）
    //参数化：将命令对象作为参数传入Invoker
    Controller player(cmdMissible, cmdBomb, cmdMoveLeft, cmdMoveRight);

    player.bomb();
    player.missible();
    player.moveLeft();
    player.moveRight();

    //为什么不直接fighter.bomb()之类的呢?
    //有时当发出命令后，我们只关心任务是否完成？但任务具体由哪个Fighter执行
    //并不是我们关心的.如果直接调用，意味着命令的发出者直接叫某个具体的Fighter去做
    //这样两者的耦合太紧.利用命令模式可以将两者解耦。

    return 0;
}