工厂模式

//
//  main.cpp
//  test
//
//  Created by sun on 15/11/14.
//  Copyright (c) 2015年 sun. All rights reserved.
//

#include <iostream>
using namespace std;


int main(int argc, const char * argv[])
{

    int a;
    printf("请输入数字a：\n");
    scanf("%d",&a);
    
    int symbol;
    printf("请输入运算符（＋－＊／）：\n");

    scanf("%d",&symbol);
    
    printf("请输入数字b：\n");
    int b;
    scanf("%d",&b);
    cout<<"result:";
    switch (symbol) {
        case 1:
            cout<<a+b<<endl;
            break;
        case 2:
            cout<<a-b<<endl;
            break;
        case 3:
            cout<<a*b<<endl;
            break;
        case 4:
            cout<<a/b<<endl;
            break;
        default:
            break;
    }
    
    return 0;
}

工厂模式

//
//  main.cpp
//  test
//
//  Created by sun on 15/11/14.
//  Copyright (c) 2015年 sun. All rights reserved.
//

#include <iostream>
using namespace std;
class Operation
{

public:
    double _a;
    double _b;
    Operation()
    {

    }

    virtual double GetResult()
    {
        double result=0;
        return result;
    }

    
};

class OperationAdd:public Operation
{
  
public:

    OperationAdd()
    {
        Operation();
    }
   double GetResult ()
    {
        return _a+_b;
    }
};

class OperationSub:public Operation
{
public:
    OperationSub()
    {
        Operation();
    }
    double GetResult ()
    {
        return _a-_b;
    }
};

class OperationFactory
{
public:
    static Operation* create(int operate)
    {
        Operation* oper;
        switch (operate) {
            case 1:
                oper=new OperationAdd();
                break;
            case 2:
                oper=new OperationSub();
                break;
            default:
                break;
        }
        return oper;
    }
};

int main(int argc, const char * argv[])
{
    Operation* oper;
    oper=OperationFactory::create(2);
    oper->_a=1;
    oper->_b=3;
    cout<<oper->GetResult()<<endl;
    return 0;
}