Update mediator pattern examples

Author: nemanjarogic

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/AirTrafficControlExecutor.cs

@@ -10,14 +10,14 @@ public static void Execute()
     {
         ConsoleExtension.WriteSeparator("Air traffic control example");
 
-        var airTraficControl = new FrankfurtAirTrafficControl();
+        var airTrafficControl = new FrankfurtAirTrafficControl();
 
-        // Register flights to air trafic control
-        var flight1 = new AirbusA320("ARB320", 28000, airTraficControl);
-        var flight2 = new Boeing737("BNG737", 29000, airTraficControl);
-        var flight3 = new Boeing777("BNG777", 35000, airTraficControl);
+        var flight1 = new AirbusA320("ARB320", 28000, airTrafficControl);
+        var flight2 = new Boeing737("BNG737", 29000, airTrafficControl);
+        var flight3 = new Boeing777("BNG777", 35000, airTrafficControl);
+        Console.WriteLine($"\nAir traffic control has registered aircraft with the call signs {flight1.CallSign}, {flight2.CallSign} and {flight3.CallSign}.");
 
         Console.WriteLine($"\nChanging altitude for {flight1.CallSign}...");
         flight1.Altitude += 1000;
     }
-}
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Components/AirbusA320.cs

@@ -10,11 +10,5 @@ public AirbusA320(string callSign, int currentAltitude, IAirTrafficControl atc)
     {
     }
 
-    public override int SeatingCapacity
-    {
-        get
-        {
-            return 180;
-        }
-    }
-}
+    public override int SeatingCapacity => 180;
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Components/Boeing737.cs

@@ -10,11 +10,5 @@ public Boeing737(string callSign, int currentAltitude, IAirTrafficControl atc)
     {
     }
 
-    public override int SeatingCapacity
-    {
-        get
-        {
-            return 143;
-        }
-    }
-}
+    public override int SeatingCapacity => 143;
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Components/Boeing777.cs

@@ -10,11 +10,5 @@ public Boeing777(string callSign, int currentAltitude, IAirTrafficControl atc)
     {
     }
 
-    public override int SeatingCapacity
-    {
-        get
-        {
-            return 368;
-        }
-    }
-}
+    public override int SeatingCapacity => 368;
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Components/Common/Aircraft.cs

@@ -4,41 +4,39 @@ namespace MediatorLibrary.AirTrafficControlExample.Components.Common;
 
 public abstract class Aircraft
 {
-    private readonly IAirTrafficControl _airTraficControl;
+    private readonly IAirTrafficControl _airTrafficControl;
     private int _currentAltitude;
 
-    protected Aircraft(string callSign, int currentAltitude, IAirTrafficControl airTraficControl)
+    protected Aircraft(string callSign, int currentAltitude, IAirTrafficControl airTrafficControl)
     {
-        _airTraficControl = airTraficControl;
-        _airTraficControl.RegisterAircraftUnderGuidance(this);
-
         CallSign = callSign;
+
+        // In this example, IAirTrafficControl interface is passed to components and components are responsible to register themselves to the mediator.
+        // Be careful with this approach, since the object that is passed to the mediator (this) might not be fully initialized.
+        // This might not be the best approach for the AirTrafficControlExample, but it's shown for demo purposes as one of possibilities.
+        // Take a look at GroupChatExample for a different approach.
+        _airTrafficControl = airTrafficControl;
+        _airTrafficControl.RegisterAircraftUnderGuidance(this);
         Altitude = currentAltitude;
     }
 
     public abstract int SeatingCapacity { get; }
 
-    public string CallSign { get; private set; }
+    public string CallSign { get; }
 
     public int Altitude
     {
-        get
-        {
-            return _currentAltitude;
-        }
+        get => _currentAltitude;
         set
         {
             _currentAltitude = value;
-            Console.WriteLine($"Aircraft with call sign {CallSign} flies at {_currentAltitude} feet.");
+            Console.WriteLine($"Aircraft with the call sign {CallSign} flies at {_currentAltitude} feet.");
 
-            _airTraficControl.ReceiveAircraftLocation(this);
+            _airTrafficControl.ReceiveAircraftLocation(this);
         }
     }
 
-    public void Climb(int heightToClimb)
-    {
-        Altitude += heightToClimb;
-    }
+    public void Climb(int heightToClimb) => Altitude += heightToClimb;
 
     public override bool Equals(object obj)
     {
@@ -48,17 +46,12 @@ public override bool Equals(object obj)
         }
 
         var incoming = (Aircraft)obj;
-        return CallSign.Equals(incoming.CallSign);
+        return CallSign.Equals(incoming.CallSign, StringComparison.Ordinal);
     }
 
-    public override int GetHashCode()
-    {
-        return CallSign.GetHashCode();
-    }
+    public override int GetHashCode() => CallSign.GetHashCode();
 
-    public void WarnOfAirspaceIntrusionBy(Aircraft aircraft)
-    {
-        // Do something in response to the warning
-        Console.WriteLine($"Aircraft {CallSign} has airspace intrusion by {aircraft.CallSign}.");
-    }
-}
+    public void WarnOfAirspaceIntrusionBy(Aircraft aircraft) =>
+        // Do something in response to the warning.
+        Console.WriteLine($"Aircraft {CallSign} has received notification about airspace intrusion by {aircraft.CallSign}.");
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Mediators/Common/IAirTrafficControl.cs

@@ -5,6 +5,5 @@ namespace MediatorLibrary.AirTrafficControlExample.Mediators.Common;
 public interface IAirTrafficControl
 {
     void ReceiveAircraftLocation(Aircraft reportingAircraft);
-
     void RegisterAircraftUnderGuidance(Aircraft aircraft);
-}
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/AirTrafficControlExample/Mediators/FrankfurtAirTrafficControl.cs

@@ -5,27 +5,32 @@ namespace MediatorLibrary.AirTrafficControlExample.Mediators;
 
 public class FrankfurtAirTrafficControl : IAirTrafficControl
 {
-    private readonly IList<Aircraft> _aircraftsUnderGuidance = new List<Aircraft>();
+    private readonly Dictionary<string, Aircraft> _aircraftUnderGuidance = new();
 
     public void ReceiveAircraftLocation(Aircraft reportingAircraft)
     {
-        foreach (var currentAircraft in _aircraftsUnderGuidance.Where(x => x != reportingAircraft))
+        var potentiallyAffectedAircraft = _aircraftUnderGuidance
+            .Values
+            .Where(a => a.CallSign != reportingAircraft.CallSign);
+
+        foreach (var currentAircraft in potentiallyAffectedAircraft)
         {
-            if (Math.Abs(currentAircraft.Altitude - reportingAircraft.Altitude) < 1000)
+            if (Math.Abs(currentAircraft.Altitude - reportingAircraft.Altitude) >= 1000)
             {
-                Console.WriteLine($"\nAir traffic control will issue request to {reportingAircraft.CallSign} to change altitude.");
-
-                currentAircraft.WarnOfAirspaceIntrusionBy(reportingAircraft);
-                reportingAircraft.Climb(1000);
+                continue;
             }
+
+            Console.WriteLine($"\nAir traffic control will issue a warning to {reportingAircraft.CallSign} aircraft about airspace intrusion.");
+            currentAircraft.WarnOfAirspaceIntrusionBy(reportingAircraft);
+            reportingAircraft.Climb(1000);
         }
     }
 
     public void RegisterAircraftUnderGuidance(Aircraft aircraft)
     {
-        if (!_aircraftsUnderGuidance.Contains(aircraft))
+        if (!_aircraftUnderGuidance.ContainsKey(aircraft.CallSign))
         {
-            _aircraftsUnderGuidance.Add(aircraft);
+            _aircraftUnderGuidance.Add(aircraft.CallSign, aircraft);
         }
     }
-}
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/Executor.cs

@@ -13,4 +13,4 @@ public override void Execute()
         AirTrafficControlExecutor.Execute();
         GroupChatExecutor.Execute();
     }
-}
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/GroupChatExample/Components/Common/User.cs

@@ -4,22 +4,18 @@ namespace MediatorLibrary.GroupChatExample.Components.Common;
 
 public abstract class User
 {
-    protected IGroupChatMediator _mediator;
+    protected IGroupChatMediator? _mediator;
     protected string _name;
 
-    public User(string name)
+    protected User(string name)
     {
         _name = name;
     }
 
     public string Name => _name;
 
-    public void SetMediator(IGroupChatMediator mediator)
-    {
-        _mediator = mediator;
-    }
+    public void SetMediator(IGroupChatMediator mediator) => _mediator = mediator;
 
     public abstract void Send(string message);
-
     public abstract void Receive(string message);
-}
+}

src/BehavioralPatterns/Mediator/MediatorLibrary/GroupChatExample/Components/ViberUser.cs

@@ -9,14 +9,17 @@ public ViberUser(string name)
     {
     }
 
-    public override void Receive(string message)
-    {
+    public override void Receive(string message) =>
         Console.WriteLine($"{_name} received the message: '{message}'");
-    }
 
     public override void Send(string message)
     {
+        if (_mediator == null)
+        {
+            return;
+        }
+
         Console.WriteLine($"{_name} is sending the message: '{message}' to the group");
         _mediator.SendMessage(message, this);
     }
-}
+}