简单工厂模式

代码来自：http://www.cnblogs.com/mydomain/archive/2011/05/06/2039502.html

#include "iostream"
#include "string"
#include "vector"
//#include "functional"
//#include "algorithm"
using namespace std;

class Operation
{
public:
    Operation(){}
    Operation(double dNumberA1, double dNumberB1)
    {
        dNumberA = dNumberA1;
        dNumberB = dNumberB1;
        dResult = 0.0;
    }
    double GetNumberA()
    {
        return dNumberA;
    }
    void SetNumberA(double dTempA)
    {
        dNumberA = dTempA;
    }
    double GetNumberB()
    {
        return dNumberA;
    }

    void SetNumberB(double dTempB)
    {
        dNumberB = dTempB;
    }

    virtual double GetResult()
    {
        return dResult;
    }
protected:
    double dNumberA;
    double dNumberB;
    double dResult;
};

class OperationAdd:public Operation
{
public:
    OperationAdd(){}
    OperationAdd(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
    double GetResult()
    {
        return dResult = dNumberA + dNumberB;
    }
};

class OperationSub:public Operation
{
public:
    OperationSub(){}
    OperationSub(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
    double GetResult()
    {
        return dResult = dNumberA - dNumberB;
    }
};

class OperationMul:public Operation
{
public:
    OperationMul(){}
    OperationMul(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
    double GetResult()
    {
        return dResult = dNumberA * dNumberB;
    }
};

class OperationDiv:public Operation
{
public:
    OperationDiv(){}
    OperationDiv(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
    double GetResult()
    {
        if (dNumberB == 0)
            throw runtime_error("除数不能为");
        return dResult = dNumberA / dNumberB;
    }
};

class OperationFactory
{
public:
    OperationFactory(string strOperaKind)
    {
        if (strOperaKind == "+")
            pOpera = new OperationAdd();
        if (strOperaKind == "-")
            pOpera = new OperationSub();
        if (strOperaKind == "*")
            pOpera = new OperationMul();
        if (strOperaKind == "/")
            pOpera = new OperationDiv();
    }
    Operation* GetOperation()
    {
        return pOpera;
    }
    ~OperationFactory()
    {
        if (pOpera)
        {
            delete pOpera;
            pOpera = NULL;
        }
    }
private:
    Operation *pOpera;
};

int main()
{
    cout << "Input two num and a operation(a number, opera, a number):" << endl;
    double dNumberA1, dNumberB1;
    string strOpera;
    cin >> dNumberA1 >> dNumberB1 >> strOpera;

    OperationFactory MyOperationFac(strOpera);
    Operation *MyOperation = MyOperationFac.GetOperation();
    MyOperation->SetNumberA(dNumberA1);
    MyOperation->SetNumberB(dNumberB1);
    cout << MyOperation->GetResult();
    return 1;
}