简单工厂模式C++实现

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">面向对象的优点：</span>

#include <iostream>
#include <string>
#include <memory>
class Operation
{
public:
Operation() = default;
Operation(double a, double b) : NumberA(a), NumberB(b) {}
double NumberA;
double NumberB;
std::string Symbol;
virtual double getResult() {
return 0;
}
};
class Add : public Operation
{
public:
Add(double a, double b) :Operation(a, b) {}
double getResult() override {
return NumberA + NumberA;
}
};
class Sub :public Operation
{
public:
Sub(double a, double b) :Operation(a, b) {}
double getResult() override {
return NumberA - NumberB;
}
};
class Multiply : public Operation
{
public:
Multiply(double a, double b) :Operation(a, b) {}
double getResult() override {
return NumberA * NumberB;
}
};
class Divide : public Operation
{
public:
Divide(double a, double b) :Operation(a, b) {}
double getResult() override {
double result = 0;
return NumberA / NumberB;
}
};
class Calculate
{
public:
Calculate() = default;
Operation oper;
Operation* createOperation(std::istream &in) {
std::string Symbol;
std::cout << "PLZ enter number a, operations, number b !" << std::endl;
in >> oper.NumberA >> Symbol >> oper.NumberB;
if (Symbol == "+")
return new Add(oper.NumberA, oper.NumberB);
if (Symbol == "-")
return new Sub(oper.NumberA, oper.NumberB);
if (Symbol == "*")
return new Multiply(oper.NumberA, oper.NumberB);
if (Symbol == "/" && oper.NumberB != 0)
return new Divide(oper.NumberA, oper.NumberB);
}
};

int main() {
Calculate cal;
Operation* op = cal.createOperation(std::cin);
double result = op->getResult();
std::cout << result << std::endl;
delete op;
return 0;
}