Observer Pattern (2)
设计模式原则：
努力使模块间为松散耦合
观察者模式：
建立对象之间一种一对多的依赖关系，使得一个对象的属性改变，其它依赖对象能够自动被通知以及更新。
示例代码：
using System;
using
System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using
System.Security.Cryptography;
namespace Hello
{
//interface
interface
Subject
{
void
RegisterObserver(Observer user);
void
RemoveObserver(Observer user);
void
NotifyObserver();
}
interface
Observer
{
void
Update();
}
interface
Display
{
void
Show();
}
//Postal
class
Postal : Subject
{
List<Observer> ObserversList;
public
Postal()
{
ObserversList = new List<Observer>();
}
public
void RegisterObserver(Observer
user)
{
ObserversList.Add(user);
}
public
void RemoveObserver(Observer
user)
{
ObserversList.Remove(user);
}
public
void NotifyObserver()
{
foreach
(Observer user in
ObserversList)
{
user.Update();
}
}
}
//user
class
User : Observer,
Display
{
string
userName;
Subject
postal;
public
User(string name, Subject
subject)
{
userName = name;
postal = subject;
}
public
void Update()
{
Console.WriteLine("{0} receive the message.", userName);
}
public
void Show()
{
Console.WriteLine("I'm user {0}", userName);
}
public
void Register()
{
postal.RegisterObserver(this);
}
public
void Remove()
{
postal.RemoveObserver(this);
}
}
//
class
Program
{
static
void Main(string[]
args)
{
Postal
postal = new Postal();
User
Mike = new User("Mike", postal);
User
Eric = new User("Eric", postal);
User
Erebus = new User("Erebus", postal);
Mike.Register();
Eric.Register();
postal.NotifyObserver();
Console.WriteLine();
Mike.Remove();
Erebus.Register();
postal.NotifyObserver();
}
}
}
