C++设计模式——策略者模式(Strategy)
作者:互联网
策略模式
策略模式主要解决枚举变化的情况,转化为一系列算法类。
enum TaxBase
{
CN_Tax,
UR_Tax,
UK_Tax,
FR_Tax
};
class SalesOrder {
private:
TaxBase tax;
public:
double CalculateTax() {
if (tax == CN_Tax) {
//...
}
else if(tax==UR_Tax){
//...
}
else if (tax == UK_Tax) {
}
}
};
上述代码以汇率计算为例,可以看到,当要扩展另一个国家的汇率计算时,需要修改枚举和SalesOrder类,加上对应的else if,这样不利于扩展,可以将枚举定义成基类,如下代码所示:
#pragma once
#ifndef STRATEGY_H
#define STRATEGY_H
#include<iostream>
using namespace std;
class TaxStrategy {
public:
virtual double CalculateTax(const double& money) = 0;
virtual ~TaxStrategy() {}
};
class CNTax :public TaxStrategy {
public:
double CalculateTax(const double& money) override{
cout << "Chinese money" << endl;
return money;
}
};
class USTax :public TaxStrategy {
public:
double CalculateTax(const double& money) override {
cout << "US money" << endl;
return money;
}
};
class UKTax :public TaxStrategy {
public:
double CalculateTax(const double& money) override {
cout << "UK money" << endl;
return money;
}
};
#endif // !STRATEGY_H
strategy.h中,改变了枚举的类型,变成继承自抽象基类的子类。测试代码如下:
#include<iostream>
using namespace std;
#include"strategy.h"
class SalesOrder {
private:
TaxStrategy* strategy;
public:
SalesOrder(TaxStrategy* strategy) {//若有多个策略,此处可以结合工厂模式
this->strategy = strategy;
}
~SalesOrder() {
delete this->strategy;
}
double Calculatetax()
{
double val = strategy->CalculateTax(10);//多态调用
cout << "success calculate" << endl;
return val;
}
};
int main()
{
SalesOrder* sale = new SalesOrder(new USTax());
sale->Calculatetax();
return 0;
}
通过这种方式,解决了上述扩展时,需要更改各种文件代码的问题,只需要添加扩展类即可,也无需修改SalesOrder 类的方法。
运行结果如下:
标签:CalculateTax,double,SalesOrder,Tax,C++,strategy,Strategy,设计模式,public 来源: https://blog.csdn.net/qq_45662588/article/details/119237486