简单工厂模式

//简单工厂模式

//父类
class Operation
{
public:
    Operation() {}
    virtual ~Operation() {};
    void setA( double a ) { m_a = a; }
    void setB( double b ) { m_b = b; }
    virtual double getResult() = 0;
protected:
    double m_a;
    double m_b;
};

//加法子类
class Add : public Operation
{
public:
    Add() {}
    virtual ~Add() {}
    virtual double getResult() { return m_a + m_b; }
};

//乘法子类
class Mul : public Operation
{
public:
    Mul() {}
    virtual ~Mul() {}
    virtual double getResult() { return m_a * m_b; }
};

//工厂类
class OperationFactory
{
public:
    OperationFactory() {}
    ~OperationFactory() {}
    static Operation* createOperation( char ch )
    {
        Operation* ope = NULL;
        switch ( ch )
        {
        case ‘+‘ :
            ope = new Add();
            break;
        case ‘*‘ :
            ope = new Mul();
            break;
        }
        return ope;
    }
};

int main()
{
    Operation *ope = OperationFactory::createOperation( ‘*‘ );
    ope->setA( 3 );
    ope->setB( 2 );
    double re = ope->getResult();

    return 0;
}