Update observer pattern examples

Author: nemanjarogic

.editorconfig

@@ -245,7 +245,7 @@ dotnet_diagnostic.CA1058.severity = error # CA1058: Types should not extend cert
 dotnet_diagnostic.CA1060.severity = error # CA1060: Move P/Invokes to NativeMethods class
 dotnet_diagnostic.CA1061.severity = error # CA1061: Do not hide base class methods
 dotnet_code_quality.CA1062.exclude_extension_method_this_parameter = true # CA1062: Validate arguments of public methods
-dotnet_diagnostic.CA1062.severity = error # CA1062: Validate arguments of public methods
+dotnet_diagnostic.CA1062.severity = warning # CA1062: Validate arguments of public methods
 dotnet_diagnostic.CA1063.severity = error # CA1063: Implement IDisposable correctly
 dotnet_diagnostic.CA1064.severity = error # CA1064: Exceptions should be public
 dotnet_diagnostic.CA1065.severity = error # CA1065: Do not raise exceptions in unexpected locations

src/BehavioralPatterns/Observer/ObserverLibrary/Executor.cs

@@ -13,4 +13,4 @@ public override void Execute()
         NewspaperExecutor.Execute();
         StockExecutor.Execute();
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/NewspaperExample/NewspaperExecutor.cs

@@ -11,14 +11,14 @@ public static void Execute()
         ConsoleExtension.WriteSeparator("Newspaper example");
 
         var dailyMail = new DailyMail();
-        dailyMail.Subscribe(new User("Emma Davis", 5));
-        dailyMail.Subscribe(new User("Mary Miller", 10));
-        dailyMail.Subscribe(new User("Ube Miller", 6));
+        dailyMail.Subscribe(new User("Emma Davis", "emma", 5));
+        dailyMail.Subscribe(new User("Mary Miller", "marry", 10));
+        dailyMail.Subscribe(new User("Ube Miller", "ube", 6));
 
         Console.WriteLine();
         dailyMail.MonthlyPrice = 6;
 
         Console.WriteLine();
         dailyMail.MonthlyPrice = 8;
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/NewspaperExample/Publishers/Common/Newspaper.cs

@@ -4,25 +4,20 @@ namespace ObserverLibrary.NewspaperExample.Publishers.Common;
 
 public abstract class Newspaper
 {
-    private readonly List<IUser> _subscribers;
-
+    private readonly Dictionary<string, IUser> _subscribers = new();
     private readonly string _name;
+
     private decimal _monthlyPrice;
 
-    public Newspaper(string name, decimal monthlyPrice)
+    protected Newspaper(string name, decimal monthlyPrice)
     {
-        _subscribers = new List<IUser>();
-
         _name = name;
         _monthlyPrice = monthlyPrice;
     }
 
     public decimal MonthlyPrice
     {
-        get
-        {
-            return _monthlyPrice;
-        }
+        get => _monthlyPrice;
         set
         {
             if (_monthlyPrice != value)
@@ -37,21 +32,21 @@ public decimal MonthlyPrice
 
     public void Subscribe(IUser user)
     {
-        _subscribers.Add(user);
+        _subscribers.Add(user.Username, user);
         Console.WriteLine($"{user.Name} is subscribed to {_name} newspaper.");
     }
 
     public void Unsubscribe(IUser user)
     {
-        _subscribers.Remove(user);
+        _subscribers.Remove(user.Username);
         Console.WriteLine($"{user.Name} is unsubscribed from {_name} newspaper.");
     }
 
     private void Notify()
     {
-        foreach (IUser user in _subscribers.ToList())
+        foreach (var user in _subscribers.Values.ToList())
         {
             user.ReportSubscriptionPriceChange(this);
         }
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/NewspaperExample/Publishers/DailyMail.cs

@@ -8,4 +8,4 @@ public DailyMail()
         : base("Daily Mail", 5)
     {
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/NewspaperExample/Subscribers/Common/IUser.cs

@@ -4,7 +4,8 @@ namespace ObserverLibrary.NewspaperExample.Subscribers.Common;
 
 public interface IUser
 {
+    public string Username { get; set; }
     public string Name { get; set; }
 
     void ReportSubscriptionPriceChange(Newspaper newspaper);
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/NewspaperExample/Subscribers/User.cs

@@ -7,12 +7,14 @@ public class User : IUser
 {
     private readonly decimal _availableMonthlySubscriptionAmount;
 
-    public User(string name, decimal availableMonthlySubscriptionAmount)
+    public User(string name, string username, decimal availableMonthlySubscriptionAmount)
     {
         Name = name;
+        Username = username;
         _availableMonthlySubscriptionAmount = availableMonthlySubscriptionAmount;
     }
 
+    public string Username { get; set; }
     public string Name { get; set; }
 
     public void ReportSubscriptionPriceChange(Newspaper newspaper)
@@ -22,4 +24,4 @@ public void ReportSubscriptionPriceChange(Newspaper newspaper)
             newspaper.Unsubscribe(this);
         }
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/StockExample/Examples/EventAndDelegate/EventAndDelegateExecutor.cs

@@ -10,7 +10,7 @@ public static void Execute()
     {
         ConsoleExtension.WriteSeparator("Stock - event and delegate example");
 
-        // Monitor a stock ticker, when particular events occur, react
+        // Monitor a stock ticker, and react when particular events occur.
         var stockTicker = new StockTicker();
 
         // Create new subscribers to listen to the stock ticker
@@ -20,7 +20,7 @@ public static void Execute()
         // Load the sample stock data
         foreach (Stock stock in StockRepository.GetData())
         {
-            stockTicker.Stock = stock;
+            stockTicker.ProcessNewStockChange(stock);
         }
     }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/StockExample/Examples/EventAndDelegate/Publishers/StockTicker.cs

@@ -2,25 +2,15 @@
 
 public class StockTicker
 {
-    private Stock _stock;
+    private Stock _lastChangedStock = Stock.Default();
+    public event EventHandler<StockChangeEventArgs>? StockChange;
 
-    public event EventHandler<StockChangeEventArgs> StockChange;
-
-    public Stock Stock
+    public void ProcessNewStockChange(Stock stock)
     {
-        get
-        {
-            return _stock;
-        }
-        set
-        {
-            _stock = value;
-            OnStockChange(new StockChangeEventArgs(_stock));
-        }
+        _lastChangedStock = stock;
+        OnStockChange(new StockChangeEventArgs(_lastChangedStock));
     }
 
-    private void OnStockChange(StockChangeEventArgs e)
-    {
+    private void OnStockChange(StockChangeEventArgs e) =>
         StockChange?.Invoke(this, e);
-    }
-}
+}

src/BehavioralPatterns/Observer/ObserverLibrary/StockExample/Examples/EventAndDelegate/StockChangeEventArgs.cs

@@ -8,4 +8,4 @@ public StockChangeEventArgs(Stock stock)
     }
 
     public Stock Stock { get; set; }
-}
+}