设计模式----Strategy(策略)

 

作用:

　　定义一系列的算法,把它们一个个封装起来, 并且使它们可相互替换.本模式使得算法可独立于使用它的客户而变化.

　　解析:

　　简而言之一句话,Strategy模式是对算法的封装.处理一个问题的时候可能有多种算法,这些算法的接口(输入参数,输出参数等)都是一致的,那么可以考虑采用Strategy模式对这些算法进行封装,在基类中定义一个函数接口就可以了.

  
 #include <iostream> using namespace std; class Strategy { public: virtual ~Strategy(){} virtual void AlgorithmInterface() = 0; }; class Context { public: Context(Strategy *pStrategy) : m_pStrategy(pStrategy) { } ~Context() { delete m_pStrategy; m_pStrategy = NULL; } void ContextInterface() { if (NULL != m_pStrategy) { m_pStrategy->AlgorithmInterface(); } } private: Strategy* m_pStrategy; }; class ConcreteStrategyA : public Strategy { public: virtual ~ConcreteStrategyA(){} virtual void AlgorithmInterface() { cout << "AlgorithmInterface Implemented by ConcreteStrategyA/n"; } }; class ConcreteStrategyB : public Strategy { public: virtual ~ConcreteStrategyB(){} virtual void AlgorithmInterface() { cout << "AlgorithmInterface Implemented by ConcreteStrategyB/n"; } }; class ConcreteStrategyC : public Strategy { public: virtual ~ConcreteStrategyC(){} virtual void AlgorithmInterface() { cout << "AlgorithmInterface Implemented by ConcreteStrategyC/n"; } }; void main() { Strategy* pStrategy = new ConcreteStrategyA(); Context* pContextA = new Context(pStrategy); pContextA->ContextInterface(); delete pContextA; pStrategy = new ConcreteStrategyB(); Context* pContextB = new Context(pStrategy); pContextB->ContextInterface(); delete pContextB; pStrategy = new ConcreteStrategyC(); Context* pContextC = new Context(pStrategy); pContextC->ContextInterface(); delete pContextC; }