[C# 디자인패턴] 제16강 옵저버 패턴

예제 코드

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace CSharp_ObserverPattern
{   
    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;
        }
        
        public override void Update()
        {
            _observerState = _subject.SubjectState;
            Console.WriteLine("Observer {0}'s new state is {1}", _name, _observerState);
        }
 
        public ConcreteSubject Subject { get; set; }        
    }
 
    abstract class Subject
    {
        private List<Observer> _observers = new List<Observer>();
 
        public void Attach(Observer observer)
        {
            _observers.Add(observer);
        }
 
        public void Detach(Observer observer)
        {
            _observers.Remove(observer);
        }
 
        public void Notify()
        {
            foreach (Observer o in _observers)
            {
                o.Update();
            }
        }
    }
 
    class ConcreteSubject : Subject
    {
        public string SubjectState { get; set; }
    }
 
    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.ReadKey();
        }
    }
}