1 简单工厂模式

 

template<class T>
 class Operation
{
public:
    Operation()
    {
        numberA = 0;
        numberB = 0;
    }
    virtual T GetResult()
    {
        T result = 0;
        return result;
    }
public:
    T numberA;
    T numberB;
};

template<class T>
class OperationAdd : public Operation<T>
{
public:
    T GetResult()
    {
        return numberA + numberB;
    }
};

template<class T>
class OperationMinus : public Operation<T>
{
public:
    T GetResult()
    {
        return numberA - numberB;
    }
};

template<class T>
class OperationMultiply : public Operation<T>
{
public:
    T GetResult()
    {
        return numberA * numberB;
    }
};

template<class T>
class OperationDivide : public Operation<T>
{
public:
    T GetResult()
    {
        return numberA / numberB;
    }
};

//工厂类
//到底要实例化谁，将来会不会增加实例化的对象，比如增加开跟运算，这是很容易变化的地方，
//应该考虑用一个单独的类来做这个创造实例的过程，这就是工厂
template<class T>
class OperationFactory
{
public:
    static Operation<T>* CreateOperate(string operate) //根据客户需要，返回一个产品
    {
        Operation<T>* oper = NULL;
        if(operate == "+")
        {
            oper = new OperationAdd<T>();
        }
        else if(operate == "-")
        {
            oper = new OperationMinus<T>();
        }
        else if(operate == "*")
        {
            oper = new OperationMultiply<T>();
        }
        else if(operate == "/")
        {
            oper = new OperationDivide<T>();
        }
        else //默认产生的是加法运算
        {
            oper = new OperationAdd<T>();
        }

        return oper;
        
    }
};

//客户端代码
int main()
{
    Operation<int>* oper = OperationFactory<int>::CreateOperate("+");
    oper->numberA = 100;
    oper->numberB = 200;
    double result = oper->GetResult();
    cout<<result<<endl;
    return 0;
}