策略模式(strategy pattern)

class calculateStrategy {
public:
    virtual int calculate(int value1, int value2) = 0;
};

class Plus : public calculateStrategy {
public:
    int calculate(int value1, int value2) { return value1 + value2;}
};

class Minus : public calculateStrategy {
public:
    int calculate(int value1, int value2) { return value1 - value2;}
};

class Calculator {
private:
    calculateStrategy *cs;
public:
    Calculator(calculateStrategy *strategy): cs(strategy) {}
    int calculate(int value1, int value2)
    {
        return cs->calculate(value1, value2);
    }
    void setStrategy(calculateStrategy *strategy) { cs = strategy; };
    ~Calculator() { delete cs; }
};

int main()
{
    calculateStrategy *strategy = new Plus;
    Calculator cal(strategy);
    cout << cal.calculate(1, 2) << endl;
    delete strategy;

    strategy = new Minus;
    cal.setStrategy(strategy);
    cout << cal.calculate(1, 2) << endl;
    //delete strategy;
}