设计模式：2策略模式

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策略模式：

制定一系列的算法，然后封装起来，使他们可以相互替换。本模式使得算法可以独立于使用它的客户而变化，算法完成的功能一样。只是各自实现存在差异。

类的划分是为了封装，分类基础是抽象，具有相同属性和功能的对象的抽象几何才是类

实例：

Cache替换算法，有先进先出，LRU，随机

main.cpp

#include <iostream>#include <stdlib.h>#include "Cache.h"#include "ReplaceAlgorithm.h"void process(){//Cache<LRU_ReplaceAlgorithm> cache;//模板实参//cache.replace();Cache<LRU_ReplaceAlgorithm> cache(FIFO);cache.replace2();}int main(int argc,char* argv[]){process();system("pause");return 0;}

Cache.h

#ifndef CACHE_H#define CACHE_H#include <memory>#include "ReplaceAlgorithm.h"enum RA_TYPE{LRU , FIFO , RANDOM};//标签template<class RA>class Cache{public:/*Cache(void);~Cache(void);void replace();*///传入标签，客户只需要知道算法的相应标签即可，不需要知道算法的具体定义。Cache(enum RA_TYPE ra){if(ra == LRU){_ptrRA.reset(new LRU_ReplaceAlgorithm());}else if(ra == FIFO){_ptrRA.reset(new FIFO_ReplaceAlgorithm());}else if(ra == RANDOM){_ptrRA.reset(new Random_ReplaceAlgorithm());}else{_ptrRA = NULL;}}Cache(void){}~Cache(void){}void replace(){_ra.replace();}void replace2(){_ptrRA->replace();}private:RA _ra;std::shared_ptr<ReplaceAlgorithm> _ptrRA;};#endif

ReplaceAlgorithm.h

#ifndef REPLACEALGORITHM_H#define REPLACEALGORITHM_Hclass ReplaceAlgorithm{public:ReplaceAlgorithm(void);virtual ~ReplaceAlgorithm(void);virtual void replace() = 0;};class FIFO_ReplaceAlgorithm : public ReplaceAlgorithm{public:FIFO_ReplaceAlgorithm(void);~FIFO_ReplaceAlgorithm(void);void replace();};class LRU_ReplaceAlgorithm : public ReplaceAlgorithm{public:LRU_ReplaceAlgorithm(void);~LRU_ReplaceAlgorithm(void);void replace();};class Random_ReplaceAlgorithm : public ReplaceAlgorithm{public:Random_ReplaceAlgorithm(void);~Random_ReplaceAlgorithm(void);void replace();};#endif

ReplaceAlgorithm.cpp

#include "ReplaceAlgorithm.h"#include <iostream>using namespace std;ReplaceAlgorithm::ReplaceAlgorithm(void){}ReplaceAlgorithm::~ReplaceAlgorithm(void){}FIFO_ReplaceAlgorithm::FIFO_ReplaceAlgorithm(){}FIFO_ReplaceAlgorithm::~FIFO_ReplaceAlgorithm(){}void FIFO_ReplaceAlgorithm::replace(){cout <<"先进先出算法" << endl;}LRU_ReplaceAlgorithm::LRU_ReplaceAlgorithm(){}LRU_ReplaceAlgorithm::~LRU_ReplaceAlgorithm(){}void LRU_ReplaceAlgorithm::replace(){cout <<"最近最少使用算法" << endl;}Random_ReplaceAlgorithm::Random_ReplaceAlgorithm(){}Random_ReplaceAlgorithm::~Random_ReplaceAlgorithm(){}void Random_ReplaceAlgorithm::replace(){cout <<"随机算法" << endl;}

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