第13章 结构型模式—享元模式

//结构型模式：享元模式
//场景：围棋软件设计。
//内部状态——围棋棋子数量多，但分只为两类：白棋和黑棋。
//          有颜色、大小、形态等属性，是可共享的对象。
//外部状态——棋子在棋盘中的位置。

#include <iostream>
#include <string>
#include <map>

using namespace std;

//************************************享元类**************************
class Coordinate; //前向声明

//享元抽象类
class ChessFlyweight
{
public:
    virtual string& getColor() = 0;
    virtual void setColor(string color) = 0;
    
    //显示棋子在棋盘中的位置
    //可以通过这个接口，将外部状态传入享元对象中
    virtual void display(Coordinate& c) = 0;
};

//非享元对象：UnsharedConcreteFlyweight（外部状态）
class Coordinate
{
    int x,y;
public:
    Coordinate(int x, int y){this->x = x;this->y = y;}
    int getX(){return x;}
    void setX(int x){this->x = x;}

    int getY(){return y;}
    void setY(int x){this->y = y;}        
};

//享元对象：ConcreteFlyweight（内部状态）
class ConcreteChess : public ChessFlyweight
{
private:
    string color;
public:
    ConcreteChess(string color){this->color = color;} 
    string& getColor() {return color;}
    void setColor(string color){this->color = color;}
    
    void display(Coordinate& c)
    {
        cout << "Chess‘s Color: " << color << endl; 
        cout << "Position: x = " << c.getX() << " y = " << c.getY() << endl;
    }
};

//************************************享元工厂类**************************
class ChessFlyweightFactory
{
private:
    static map<string,ChessFlyweight*> chessMap;
public:
    static ChessFlyweight* getChess(string color)
    {
        ChessFlyweight* ret = chessMap[color]; 
        if(ret == NULL)
        {
            ret = new ConcreteChess(color);
            chessMap[color] = ret;
        }
        return ret;   
    }

    static void clear()
    {
        map<string, ChessFlyweight*>::iterator iter = chessMap.begin();
        while(iter != chessMap.end())
        {
            delete iter->second;
            cout <<iter->second << endl;
            ++iter;
        }
        chessMap.clear();
    }    
};

map<string,ChessFlyweight*> ChessFlyweightFactory::chessMap;

int main()
{
    ChessFlyweight* chess1 = ChessFlyweightFactory::getChess("black");
    ChessFlyweight* chess2 = ChessFlyweightFactory::getChess("black");
    ChessFlyweight* chess3 = ChessFlyweightFactory::getChess("white");
    
    cout << "chess1 = " << chess1 << endl;
    cout << "chess2 = " << chess2 << endl;
    cout << "chess3 = " << chess3 << endl;
    
    //增加外部状态的处理
    cout << "extrinsic state: " << endl;
    Coordinate c1(10, 10);
    Coordinate c2(20, 20);
    Coordinate c3(30, 30);
    
    chess1->display(c1);
    chess2->display(c2);
    chess3->display(c3);
    
    //删除享元池中的对象
    ChessFlyweightFactory::clear();
    
    return 0;
}