Modifying the observer pattern by adding delegates and event to it

Author: Edrisym

DesignPattern.Observer/IPublisher.cs

@@ -1,9 +1,10 @@
 namespace DesignPattern.Observer;
+public delegate void Notify(string message);
 
-// The Subject
 public interface IPublisher
 {
-    void Subscribe(ISubscriber subscriber);
-    void UnSubscribe(ISubscriber subscriber);
+    event Notify OnNotify;
+    void Subscribe(Notify subscriber);
+    void UnSubscribe(Notify subscriber);
     void Notify();
 }

DesignPattern.Observer/Program.cs

@@ -1,21 +1,19 @@
 using DesignPattern.Observer;
 
-public class Program
-{
-    public static void Main()
-    {
-        var publisher = new Publisher();
+var publisher = new Publisher();
 
-        var subscriber1 = new Subscriber1();
-        var subscriber2 = new Subscriber2();
+var subscriber1 = new Subscriber1();
+var subscriber2 = new Subscriber2();
 
-        publisher.Subscribe(subscriber1);
-        publisher.Subscribe(subscriber2);
+    publisher.Subscribe(subscriber1.Update);
+    publisher.Subscribe(subscriber2.Update);
 
-        publisher.PublishPost("New post");
+    // publisher.OnNotify += subscriber1.Update;
+    // publisher.OnNotify += subscriber2.Update;
 
-        publisher.UnSubscribe(subscriber1);
-
-        publisher.PublishPost("New post");
-    }
-}
+    //
+    publisher.PublishPost("New post published!!");
+    //
+    publisher.UnSubscribe(subscriber1.Update);
+    // // publisher.OnNotify -= subscriber1.Update;
+    publisher.PublishPost("Another post published!!");

DesignPattern.Observer/Publisher.cs

@@ -1,22 +1,26 @@
 namespace DesignPattern.Observer;
 
 
+
 public class Publisher : IPublisher
 {
-    private readonly List<ISubscriber> _subscribers = [];
+    // private readonly List<ISubscriber> _subscribers = [];
 
-    private string _state; // Can be anything that happens or gets updated
+    private string _state;
+    public event Notify? OnNotify;
 
-    public void Subscribe(ISubscriber member)
+    public void Subscribe(Notify subscriber)
     {
         Console.WriteLine("the subscriber has subscribed...");
-        _subscribers.Add(member);
+        // _subscribers.Add(member);
+        OnNotify += subscriber;
     }
 
-    public void UnSubscribe(ISubscriber member)
+    public void UnSubscribe(Notify subscriber)
     {
         Console.WriteLine("the subscriber has unsubscribed...");
-        _subscribers.Remove(member);
+        // _subscribers.Remove(member);
+        OnNotify -= subscriber;
     }
 
     public void PublishPost(string state)
@@ -27,9 +31,11 @@ public void PublishPost(string state)
 
     public void Notify()
     {
-        foreach (var member in _subscribers)
-        {
-            member.Update(_state);
-        }
+        OnNotify?.Invoke(_state);
+        // foreach (var member in _subscribers)
+        // {
+        //     Console.WriteLine();
+        //     // member.Update(_state);
+        // }
     }
 }

DesignPattern.Observer/Subscriber1.cs

@@ -12,6 +12,6 @@ public void Update(string state)
 
     private void GetNotify()
     {
-        Console.WriteLine($"Subscriber1 was notified - {_state}");
+        Console.WriteLine($"Subscriber 1 was notified - {_state}");
     }
 }

DesignPattern.Observer/Subscriber2.cs

@@ -12,6 +12,6 @@ public void Update(string state)
 
     private void GetNotify()
     {
-        Console.WriteLine($"Subscriber2 was notified - {_state}");
+        Console.WriteLine($"Subscriber 2 was notified - {_state}");
     }
 }