大话设计模式学习 C++

工厂模式

#include "bits/stdc++.h"
using namespace std;

//基类 进行操作
class Operation
{
protected:
    /* data */
    double _numberA = 0;
    double _numberB = 0;

public:
    virtual double getResult() = 0;
    void setNumber(double A, double B)
    {
        _numberA = A;
        _numberB = B;
    };
    ~Operation(){};
};
//子类 进行具体的运算操作
class OpAdd : public Operation
{
public:
    double getResult() override
    {
        return _numberA + _numberB;
    }
};

class OpSub : public Operation
{
public:
    double getResult() override
    {
        return _numberA - _numberB;
    }
};

class OpMul : public Operation
{
public:
    double getResult() override
    {
        return _numberA * _numberB;
    }
};

class OpDiv : public Operation
{
public:
    double getResult() override
    {
        if (_numberB == 0)
            throw "除数不能为0";
        return _numberA / _numberB;
    }
};

//工厂类 用于产生对应类型的对象 将变化限制在工厂中
class OpFactory
{
public:
    static Operation *createFactory(char opreate)
    {
        Operation *oper = nullptr;
        switch (opreate)
        {
        case '+':
            oper = new OpAdd();
            break;
        case '-':
            oper = new OpSub();
            break;
        case '*':
            oper = new OpMul();
            break;
        case '/':
            oper = new OpDiv();
            break;
        default:
            break;
        }
        return oper;
    }
};

//界面逻辑
int main()
{
    string op;
    double a, b;
    cin >> a >> op >> b;
    Operation *oper = OpFactory::createFactory(op[0]);
    oper->setNumber(a, b);
    try
    {
        cout << "运算结果为: " << oper->getResult();
    }
    catch (const char *msg)
    {
        cout << msg;
    }
    return 0;
}