简单工厂模式

【1】什么是简单工厂模式？

核心思想：创建一个具体工厂角色，根据客户端输入的条件产生相应的实体对象，然后由不同实体对象对virtual操作方法的调用得到不同的结果。

理解：根据条件生成不同的实例。利用多态的特性，调用同名方法，不同的实例将得到不同的结果。

【2】代码示例如下：

代码如下：

#include <iostream>
#include <string>
using namespace std;

/*
* 运算基类
*/
class Operation
{
protected:
    double m_numberA;
    double m_numberB;

public:
    double getNumberA()
    {
        return m_numberA;
    }

    void setNumberA(double dValue)
    {
        m_numberA = dValue;
    }

    double getNumberB()
    {
        return m_numberB;
    }

    void setNumberB(double dValue)
    {
        m_numberB = dValue;
    }

    virtual double getResult()
    {
        return 0;
    }
};

/*
* 加法运算子类
*/
class addOperation : public Operation
{
public:
    double getResult()
    {
        return m_numberA + m_numberB;
    }
};

/*
* 减法运算子类
*/
class subOperation : public Operation
{
public:
    double getResult()
    {
        return m_numberA - m_numberB;
    }
};

/*
* 乘法运算子类
*/
class mulOperation : public Operation
{
public:
    double getResult()
    {
        return m_numberA * m_numberB;
    }
};

/*
* 除法运算子类
*/
class divOperation : public Operation
{
public:
    double getResult()
    {
        if (0 == m_numberB)
        {
            return 0; // 无意义
        }

        return m_numberA / m_numberB;
    }
};

/*
* 构建简单工厂
*/
class operFactory
{
public:
    static Operation *createOperation(char c)
    {
        switch (c)
        {
        case '+':
            return (new addOperation);
        case '-':
            return (new subOperation);
        case '*':
            return (new mulOperation);
        case '/':
            return (new divOperation);
        default:
            return (new addOperation);
        }
    }
};

/*
* 客户端应用示例
*/
void main()
{
    Operation* pOper = operFactory::createOperation('+');
    pOper->setNumberA(9);
    pOper->setNumberB(99);
    cout << pOper->getResult() << endl;

    delete pOper;
    pOper = NULL;

    system("pause");
}

// run result:
/*
108
请按任意键继续. . .
*/

Good Good Study, Day Day Up.

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