简单工厂模式（simple factory pattern）

 

 

vs2005+C#+.net 2.0 

using System;
using System.Collections.Generic;
using System.Text;

namespace SimpleFactoryPattern
...{
    public class SchoolUser
    ...{
        protected string FName;
        protected string LName;
        protected string UserType;

        public void Show()
        ...{
            Console.WriteLine("First Name:" + FName);
            Console.WriteLine("Last Name:" + LName);
            Console.WriteLine("User Type" + UserType);
        }
    }

    public class SchoolPrincipal : SchoolUser
    ...{
        public SchoolPrincipal()
        ...{
            FName = "Jian";
            LName = "Yang";
            UserType = "Principal";
        }
    }

    public class SchoolTeacher : SchoolUser
    ...{
        public SchoolTeacher()
        ...{
            FName = "David";
            LName = "Terry";
            UserType = "Teacher";
        }
    }

    public class UserFactory
    ...{
        public SchoolUser GetSchoolUser(string user, string password)
        ...{
            if (user == "Principal" && password == "Principal")
                return new SchoolPrincipal();
            if (user == "Teacher" && password == "Teacher")
                return new SchoolTeacher();
            return null;
        }
    }
    class Client
    ...{
        static void Main(string[] args)
       ...{
            UserFactory uf = new UserFactory();
            SchoolUser su;
            su = uf.GetSchoolUser("Principal", "Principal");
            Console.WriteLine("=====Principal Log In=====");
            su.Show();
            su = uf.GetSchoolUser("Teacher", "Teacher");
            Console.WriteLine("======Teacher Log In======");
            su.Show();
            Console.Read();
       }
    }
}

 

优点：是客户端独立于产品的创建过程，并且在系统引入新产品时无需对客户端进行修改。

缺点：当新产品加入系统时，必须要修改工厂类，已加入必要的处理逻辑。简单工厂模式的致命弱点是处于工厂核心地位的工厂类，一旦它无法确定对哪个类进行实例化，就无法使用模式。