设计模式-策略模式

代码实现

class Strategy
{
public:
    Strategy() {}

    virtual void AlgrithmInterface() = 0;    //算法族接口

    virtual ~Strategy()
    {
        cout << "Strategy Destruction called." << endl;
    }
};

class ConcrateStrategyA : public Strategy
{
public:
    ConcrateStrategyA() {}

    virtual void AlgrithmInterface()
    {
        cout << "ConcrateStrategyA AlgrithmInterface Called." << endl;
    }

    virtual ~ConcrateStrategyA()
    {
        cout << "ConcrateStrategyA Destruction called" << endl;
    }
};

class ConcrateStrategyB : public Strategy
{
public:
    ConcrateStrategyB() {}

    virtual void AlgrithmInterface()
    {
        cout << "ConcrateStrategyB AlgrithmInterface Called." << endl;
    }

    virtual ~ConcrateStrategyB()
    {
        cout << "ConcrateStrategyB Destruction Called" << endl;
    }
};


class Context
{
public:
    Context(Strategy *pStrategy)
    {
        mStrategy = pStrategy;
    }

    void DoAction()
    {
        if (mStrategy)
        {
            mStrategy->AlgrithmInterface();
        }
    }

    void SetStrategy(Strategy *pStrategy)
    {
        mStrategy = pStrategy;
    }
    ~Context()
    {
        if (mStrategy)
        {
            delete mStrategy;
            mStrategy = NULL;
        }
    }
private:
    Strategy *mStrategy;
};

int _tmain(int argc, _TCHAR* argv[])
{
    ConcrateStrategyA *strategyA = new ConcrateStrategyA;
    ConcrateStrategyB *strategyB = new ConcrateStrategyB;
    Context context(strategyA);
    context.DoAction();

    context.SetStrategy(strategyB);
    context.DoAction();

    delete strategyA;
    strategyA = NULL;
    delete strategyB;
    strategyB = NULL;
    getchar();
    return 0;
}

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