原文链接：https://blog.csdn.net/qq_39355828/article/details/110840802 (opens new window)

设计模式

1.简单工厂模式

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简单工厂模式：父类有两个参数，计算结果参数需要重载。有四个类继承父类 重写了结果的计算方式。工厂类根据传进来的参数进行类的生成。生成的类返回给主函数，这里使用引用方式。用到了父类一定是子类的概念 可以指代不同的工厂生成的子类。

/*所有用到类的代码*/
#ifndef ADD_SUB_MUI_DIV_H
#define ADD_SUB_MUI_DIV_H
#include<string.h>
class Operation{
public : double _numbleA=0;
public : double _numberB=0;
public : void setValue(double _VnumbleA,double _VnumbleB)
    {
        _numbleA=_VnumbleA;
        _numberB=_VnumbleB;
    }
public: virtual double GetResult()//含有纯虚函数的类为抽象类，抽象类不能实例化对象
    {
        double result =0;
        return result;
    }
};
class OperationAdd :public Operation {
public : double GetResult()
    {
        double result =0;
        result=_numbleA+_numberB;
        return result;
    }
};
class OperationSUB:public Operation{
public : double GetResult()
    {
        double result =0;
        result=_numbleA-_numberB;
        return result;
    }
};
class OperationMUI:public Operation{
public :  double GetResult()
    {
        double result =0;
        result=_numbleA*_numberB;
        return result;
    }
};
class OperationDIV:public Operation{
public : double GetResult()
    {
        double result =0;
        result=_numbleA/_numberB;
        return result;
    }
};
class OperationFactory
{
public : Operation* CreateOperate (char operate)
    {   Operation *oper=NULL;
        switch(operate)
        {
            case '+':
            oper=new OperationAdd();

                break;
            case '-':
                oper=new OperationSUB();
                break;
            case '*':
                oper=new OperationMUI();
                break;
            case '/':
                oper=new OperationDIV();
                break;

        }
        return oper;
    }
};
#endif

主函数

#include <iostream>
#include"cmake-build-debug/ADD_SUB_MUI_DIV.h"
using namespace std;
int main() {
    OperationFactory oper;
    char opee='/';
    Operation * opop=oper.CreateOperate(opee);
    double NumberA=5,NumberB=5;
    opop->setValue(NumberA,NumberB);
    double result=opop->GetResult();
    cout<<result<<endl;
    return 0;
}