设计模式C++实现---简单工厂模式

头文件中对类的声明：

#ifndef _MY_HEAD_
#define _MY_HEAD_
class operation//opreation class
{
    private:
        double num1;
        double num2;
    public:
        double getNum1();
        double getNum2();
        void setNum1(double num);
        void setNum2(double num);
        virtual double getResult()=0;    //纯虚函数，有子类去实现具体的运算过程
};
class operation_add : public operation//+
{
    public:
        operation_add();
        virtual double getResult();
};
class operation_sub: public operation//-
{
    public:
        operation_sub();
        virtual double getResult();
};
class operation_mult: public operation//*
{
    public:
        operation_mult();
        virtual double getResult();
};
class operation_div: public operation// /
{
    public:
        operation_div();
        virtual double getResult();
};
class FactoryOperation
{
    public:
        static operation* creatOperation(char s);
};
#endif

类的定义：

#include"operation.h"

double operation::getNum1()
{
    return num1;
}
double operation::getNum2()
{
    return num2;
}
void operation::setNum1(double num)
{
    this->num1 = num;
}
void operation::setNum2(double num)
{
    this->num2 = num;
}
double operation_add::getResult()
{
    return this->getNum1()+this->getNum2();
}
operation_add::operation_add(){
}

double operation_sub::getResult()
{
    return this->getNum1()- this->getNum2();
}
operation_sub::operation_sub(){
}
double operation_mult::getResult()
{
    return this->getNum1()*this->getNum2();
}
operation_mult::operation_mult(){
}

double operation_div::getResult()
{
    return this->getNum1()/this->getNum2();
}
operation_div::operation_div(){
}

operation *FactoryOperation::creatOperation(char s)
{
    operation *oper = nullptr;
    switch(s)
    {
        case '+':
            oper = new operation_add();
            break;
        case '-':
            oper = new operation_sub();
            break;
        case '*':
            oper = new operation_mult();
            break;
        case '/':
            oper = new operation_div();
            break;
    }
    return oper;
}