代码实现 

//simpleFactory.h
#ifndef _SimpleFactory_H_
#define _SimpleFactory_H_#include <iostream>
#include <exception>
#include <string>using namespace std;class Operation {
protected:double _numberA = 0;double _numberB = 0;
public:Operation() {}Operation(double a, double b) {_numberA = a;_numberB = b;}Operation& operator=(Operation& p) {_numberA = p.getNumberA();_numberB = p.getNumberB();}double getNumberA() {return _numberA;}void setNumberA(double value) {_numberA = value;}double getNumberB() {return _numberB;}void setNumberB(double value) {_numberB = value;}virtual double GetResult() {return 0;}
};
class OperationAdd :public Operation {double GetResult() {double result = 0;result = _numberA + _numberB;return result;}
};
class OperationSub :public Operation {double GetResult() {double result = 0;result = _numberA - _numberB;return result;}
};
class OperationMul :public Operation {double GetResult() {double result = 0;result = _numberA * _numberB;return result;}
};
class OperationDiv :public Operation {double GetResult() {double result = 0;try {result = _numberA / _numberB;}catch (exception&) {cout << "发生除0异常" << endl;}return result;}
};
class OperationFactory {
public:static Operation* createOperation(char operate) {Operation* oper;switch (operate) {case '+':oper = new OperationAdd();break;case '-':oper = new OperationSub();break;case '*':oper = new OperationMul();break;case '/':oper = new OperationDiv();break;}return oper;}
};
#endif //_SimpleFactory_H_

UML图

总结

可以发现，简单工厂类是制造运算类的对象的，并且只需要传递关键参数给简单工厂类的方法（通常为静态方法），就可以创造出相应的对象出来。
故简单工厂适用于工厂类负责创建的对象较少的场景，且客户端只需要传入工厂类的参数，对于如何创建对象不需要关心。

收获

1.可以通过封装、继承、多态把程序的耦合度降低。
2.可以通过设计模式使程序变得更加灵活，易于修改，并且易于复用。
3.简单工厂模式适用创建对象少的情况，需要传参来指定需要的对象（产品）。