C++设计模式:策略模式
策略模式就是将多种算法类进行封装,每个算法类都继承于一个基类A,然后重写一个新类B,在这个新类里定义一个基类A的对象,然后在新类B的构造函数中对基类A的对象进行赋值,这种方法需要对B的构造函数传参数,如果需要不传参数,则可以写成模板的形式,以下是代码:
#include <iostream>
using namespace std;
class ReplaceAlgorithm
{
public:
ReplaceAlgorithm()
{
}
~ReplaceAlgorithm()
{
}
public:
virtual void Replace() = 0;
};
//three replace algorithm
class LRU_ReplaceAlgorithm:public ReplaceAlgorithm
{
public:
void Replace()
{
cout<<"Least Recently Used replace algorithm"<<endl;
}
};
class FIFO_ReplaceAlogrithm:public ReplaceAlgorithm
{
public:
void Replace()
{
cout<<"First in Fist out replace algorithm"<<endl;
}
};
class Random_ReplaceAlgorithm:public ReplaceAlgorithm{
public:
void Replace()
{
cout<<"Random replace algorithm"<<endl;
}
};
/*
enum RA {LRU, FIFO, RANDOM};
class Cache
{
private:
ReplaceAlgorithm * m_ra;
public:
Cache(enum RA ra)
{
if(ra == LRU)
{
m_ra = new LRU_ReplaceAlgorithm();
}
else if(ra == FIFO)
{
m_ra = new FIFO_ReplaceAlogrithm();
}
else if(ra == RANDOM)
{
m_ra = new Random_ReplaceAlgorithm();
}
else
m_ra = NULL;
}
~Cache()
{
delete m_ra;
}
void Replace()
{
m_ra->Replace();
}
};
*/
template <class RA>
class Cache
{
private:
RA m_ra;
public:
Cache()
{
}
~Cache()
{
}
void Replace()
{
m_ra.Replace();
}
};
int main()
{
cout<<"start to test"<<endl;
//Cache cache(LRU);
Cache<Random_ReplaceAlgorithm> cache;
cache.Replace();
return 0;
}