C++設計模式：工廠模式

工廠模式：工廠模式是在簡單工廠模式的基礎上，將工廠類也抽象爲一個接口，然後根據不同要求，編寫具體的生產對象的工廠子類。

代碼實現思路：建立操作基類和工廠基類，然後再建立具體的操作子類繼承操作基類；建立具體的工廠子類繼承工廠基類。因此，當要增加新的操作時，只需要增加此功能的操作子類和工廠子類即可，而不用再修改原有代碼邏輯，體現了C++的面向對象的思想。

代碼：

#include<iostream>

using namespace std;



class Operation
{
protected:
    double _numberA;
    double _numberB;

public:
    Operation() :_numberA(0.0), _numberB(0.0)
    {}
    void SetNumberA(double number)
    {
        _numberA = number;
    }
    void SetNumberB(double number)
    {
        _numberB = number;
    }

    double GetNumberA()
    {
        return _numberA;
    }
    double GetNumberB()
    {
        return _numberB;
    }
    virtual double GetResult() = 0;
};

class OperationAdd :public Operation
{
    double GetResult()
    {
        return _numberA + _numberB;
    }
};

class OperationSub :public Operation
{
    double GetResult()
    {
        return _numberA - _numberB;
    }
};

class OperationMul :public Operation
{
    double GetResult()
    {
        return _numberA*_numberB;
    }
};

class OperationDiv :public Operation
{
    double GetResult()
    {
        if (abs(_numberB) > 0.0001)
            return _numberA / _numberB;
        else
            throw("除數不能爲0");
    }
};


class IFactory
{
public:

    virtual Operation* CreateOperation()=0;
};


class AddFactory :public IFactory
{
public:
    Operation* CreateOperation()
    {
        return new OperationAdd();
    }
};

class SubFactory :public IFactory
{
public:
    Operation* CreateOperation()
    {
        return new OperationSub();
    }
};

class MulFactory :public IFactory
{
public:
    Operation* CreateOperation()
    {
        return new OperationMul();
    }
};

class DivFactory :public IFactory
{
public:
    Operation* CreateOperation()
    {
        return new OperationDiv();
    }
};

int main()
{

    IFactory* operFactory = new AddFactory();
    Operation*oper = operFactory->CreateOperation();


    oper->SetNumberA(10);
    oper->SetNumberB(56);
    double result = oper->GetResult();

    cout << result << endl;

    return 0;
}