設計模式觀察者模式
觀察者用例圖
代碼
class Program
{
static void Main(string[] args)
{
ConcreteSubject s = new ConcreteSubject();
s.Attach(new ConcreteObserver(s, "X"));
s.Attach(new ConcreteObserver(s, "Y"));
s.Attach(new ConcreteObserver(s, "Z"));
s.SubjectState = "ABC";
s.Notify();
Console.Read();
}
}
abstract class Subject
{
private IList<Observer> observers = new List<Observer>();
//增加观察者
public void Attach(Observer observer)
{
observers.Add(observer);
}
//移除观察者
public void Detach(Observer observer)
{
observers.Remove(observer);
}
//通知
public void Notify()
{
foreach (Observer o in observers)
{
o.Update();
}
}
}
//具体通知者
class ConcreteSubject : Subject
{
private string subjectState;
//具体通知者状态
public string SubjectState
{
get { return subjectState; }
set { subjectState = value; }
}
}
abstract class Observer
{
public abstract void Update();
}
class ConcreteObserver : Observer
{
private string name;
private string observerState;
private ConcreteSubject subject;
public ConcreteObserver(
ConcreteSubject subject, string name)
{
this.subject = subject;
this.name = name;
}
//更新
public override void Update()
{
observerState = subject.SubjectState;
Console.WriteLine("观察者{0}的新状态是{1}",
name, observerState);
}
public ConcreteSubject Subject
{
get { return subject; }
set { subject = value; }
}
}
