设计模式[7]-Strategy

Type: Behavioral

Strategy模式：定义一系列的算法，封装每一个，使他们实现通用。让算法相对于使用他的clients可以独立地变化。

#include <iostream>
using namespace std;  

class Strategy
{
public:
    virtual void execute() = 0;
};   

class ConcreteStrategyA: public Strategy
{
public:
    void execute()
    {
        cout<<"ConcreteStrategyA executed"<<endl;
    }
};  

class ConcreteStrategyB: public Strategy
{
public:
    void execute()
    {
        cout<<"ConcreteStrategyB executed"<<endl;
    }
};  

class Context
{
public:
    Context (Strategy* pStrategy): m_pStrategy(pStrategy){};
    void setStrategy(Strategy* pStrategy)
    {
        m_pStrategy = pStrategy;
    }
    void invoke()
    {
        if(m_pStrategy != NULL)
            m_pStrategy->execute();
    }
private:
    Strategy* m_pStrategy;
};  

int main()
{
    Strategy* pStrategy = new ConcreteStrategyA();
    Context*  pContext  = new Context(pStrategy);
    pContext->invoke();
    pStrategy = new ConcreteStrategyB();
    pContext->setStrategy(pStrategy);
    pContext->invoke();  

    system("pause");
    return 0;
}