详解C++设计模式编程中策略模式的优缺点及实现

#include <iostream> 
#include <string> 
#include <memory> 
using namespace std; 
 
//strategy抽象类，用作接口 
class Strategy 
{ 
public: 
  virtual string substitute(string str)=0; 
  virtual ~Strategy() 
  { 
    cout<<" in the destructor of Strategy"<<endl; 
  } 
}; 
 
class ChineseStrategy:public Strategy 
{ 
public: 
  string substitute(string str) 
  { 
    int index=str.find("520"); 
    string tempstr=str.replace(index,3,"我爱你"); 
    return tempstr; 
  } 
  ~ChineseStrategy() 
  { 
    cout<<"in the destructor of ChineseStrategy"<<endl; 
  } 
}; 
 
class EnglishStrategy:public Strategy 
{ 
public: 
  string substitute(string str) 
  { 
    int index=str.find("520"); 
    string tempstr=str.replace(index,3,"i love ou"); 
    return tempstr; 
  } 
  ~EnglishStrategy() 
  { 
    cout<<" in the destructor of ChineseStrategy"<<endl; 
  } 
}; 
 
//Context类 

class Translator 
{ 
private: 
  auto_ptr<Strategy> strategy; 

     //在客户代码中加入算法（stategy）类型的指针。 
public: 
  ~Translator() 
  { 
    cout<<" in the destructor of Translator"<<endl; 
  } 
  void set_strategy(auto_ptr<Strategy> strategy) 
  { 
    this->strategy=strategy; 
  } 
  string translate(string str) 
  { 
    if(0==strategy.get()) 
      return ""; 
    return strategy->substitute(str); 
  } 
}; 

#include "Strategy.h" 
 
int main(int argc, char *argv) 
{ 
  string str("321520"); 
  Translator *translator=new Translator; 
  //未指定strategy的时候 
  cout<<"No Strategy"<<endl; 
  translator->translate(str); 
  cout<<"---------------"<<endl; 
   
  //翻译成中文 
  auto_ptr<Strategy> s1(new ChineseStrategy); 
  translator->set_strategy(s1); 
  cout<<"Chinese Strategy"<<endl; 
  cout<<translator->translate(str)<<endl; 
  cout<<"---------------"<<endl; 
 
  //翻译成英文 
  auto_ptr<Strategy> s2(new EnglishStrategy); 
  translator->set_strategy(s2); 
  cout<<"English Strategy"<<endl; 
  cout<<translator->translate(str)<<endl; 
  cout<<"----------------"<<endl; 
 
  delete translator; 
  return 0; 
 
}