设计模式之-工厂方法

工厂方法模式（Factory Method）

定义一个用于创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延续到其子类中。

工厂方法模式是简单工厂的扩展，工厂方法把简单工厂的内部逻辑判断转移到了客户端进行，想要增加功能，以前是修改工厂类，现在是修改客户端。

工厂方法模式克服了简单工厂违背开放-封闭原则（软件实体应该可以扩展，但是不可以修改）的缺点，又保持了封装对象创建过程的优点。但缺点是每加一个产品，就需要加一个产品工厂的类，增加额外的开发。

    public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;
        public double NumberA
        {
            get;
            set;
        }
        public double NumberB
        {
            get;
            set;
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
    class OperationAdd:Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }
    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
　　 interface IFactory
    {
        Operation CreateOperation();
    }
　　class AddFactory:IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationAdd();
        }
    }
　　class DivFactory
    {
        public Operation CreateOperation()
        {
            return new OperationDiv();
        }
    }
//以下是客户端内代码
static void Main(string[] args)
{
　　IFactory operFactory = new AddFactory();//工厂方法模式 
　　Operation oper = operFactory.CreateOperation(); 
　　oper.NumberA = 4; 
　　oper.NumberB = 2; 
　　double result = oper.GetResult(); 
　　Console.WriteLine(result); Console.Read();
}

 

UML类图

 C++的工厂方法模式如下：

#include<iostream>
#include<string>
using namespace std;
class Producer
{
protected:
    string brand;
public:
    virtual void output()
    {
        cout << brand << "---" << "的产品" << endl;
    }
};
class Haier :public Producer
{
protected:
    string brand = "Haier";
public:
    virtual void output()
    {
        cout<<brand<<endl;
    }
};
class Midea :public Producer
{
protected:
    string brand = "Mieda";
public:
    virtual void output()
    {
        cout << brand << endl;
    }
};

class Factory
{
public:
    virtual Producer* producer() = 0;
};

class FactoryHaier :public Factory
{
public:
    Producer* producer()
    {
        return new Haier;
    }
};

class FactoryMidea :public Factory
{
public:
    Producer* producer()
    {
        return new Midea;
    }
};
int main()
{
    FactoryHaier* fh = new FactoryHaier();
    FactoryMidea* fm = new FactoryMidea();
    Producer* pro = fh->producer();
    pro->output();
    pro = fm->producer();
    pro->output();
    return 0;
}

参考至博客：(1条消息) C++实现简单工厂模式等的设计应用_坤sama的博客-CSDN博客