Add Observer Pattern

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/FormulaOne.cs

@@ -0,0 +1,33 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public class FormulaOne : ISubject
+{
+    private readonly List<IObserver> _observers = new();
+    private RacingFlag _racingFlag = RacingFlag.Green;
+
+    public void RegisterObserver(IObserver observer)
+    {
+        _observers.Add(observer);
+    }
+
+    public void UnregisterObserver(IObserver observer)
+    {
+        _observers.Remove(observer);
+    }
+
+    public void NotifyObservers()
+    {
+        _observers.ForEach(o => o.Update());
+    }
+
+    public RacingFlag GetRacingFlag()
+    {
+        return _racingFlag;
+    }
+
+    public void SetRacingFlag(RacingFlag racingFlag)
+    {
+        _racingFlag = racingFlag;
+        NotifyObservers();
+    }
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/ICar.cs

@@ -0,0 +1,7 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public interface ICar : IDisposable
+{
+    public string Name { get; }
+    string GetRacingPace();
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/IObserver.cs

@@ -0,0 +1,6 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public interface IObserver : IDisposable
+{
+    void Update();
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/ISubject.cs

@@ -0,0 +1,8 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public interface ISubject
+{
+    void RegisterObserver(IObserver observer);
+    void UnregisterObserver(IObserver observer);
+    void NotifyObservers();
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/Mercedes.cs

@@ -0,0 +1,37 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public class Mercedes : ICar, IObserver
+{
+    public string Name { get; } = "Mercedes";
+
+    private RacingFlag _flag;
+    private readonly FormulaOne _formulaOne;
+
+    public Mercedes(FormulaOne formulaOne)
+    {
+        _formulaOne = formulaOne;
+        _formulaOne.RegisterObserver(this);
+    }
+
+    public void Update()
+    {
+        _flag = _formulaOne.GetRacingFlag();
+    }
+
+    public string GetRacingPace()
+    {
+        return _flag switch
+        {
+            RacingFlag.Green => "Full speed ahead!",
+            RacingFlag.Yellow => "Slow down!",
+            RacingFlag.Red => "Stop!",
+            _ => throw new ArgumentOutOfRangeException()
+        };
+    }
+
+    public void Dispose()
+    {
+        _formulaOne.UnregisterObserver(this);
+        GC.SuppressFinalize(this);
+    }
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/RacingFlag.cs

@@ -0,0 +1,8 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public enum RacingFlag
+{
+    Green,
+    Yellow,
+    Red
+}

MadWorld/MadWorld.Frontend.Application/DesignPatterns/ObserverPattern/RedBull.cs

@@ -0,0 +1,37 @@
+namespace MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+public class RedBull : ICar, IObserver
+{
+    public string Name { get; } = "Red Bull";
+
+    private RacingFlag _flag;
+    private readonly FormulaOne _formulaOne;
+
+    public RedBull(FormulaOne formulaOne)
+    {
+        _formulaOne = formulaOne;
+        _formulaOne.RegisterObserver(this);
+    }
+
+    public void Update()
+    {
+        _flag = _formulaOne.GetRacingFlag();
+    }
+
+    public string GetRacingPace()
+    {
+        return _flag switch
+        {
+            RacingFlag.Green => "Fly away!",
+            RacingFlag.Yellow => "Go half speed!",
+            RacingFlag.Red => "Stop!",
+            _ => throw new ArgumentOutOfRangeException()
+        };
+    }
+
+    public void Dispose()
+    {
+        _formulaOne.UnregisterObserver(this);
+        GC.SuppressFinalize(this);
+    }
+}

MadWorld/MadWorld.Frontend.UI.Suite/Pages/Learn/DesignPatterns/DesignPatterns.razor

@@ -0,0 +1,3 @@
+@page "/Learn/DesignPatterns"
+
+<a href="/Learn/DesignPatterns/ObserverPattern" class="btn btn-primary">Observer Patterns</a>

MadWorld/MadWorld.Frontend.UI.Suite/Pages/Learn/DesignPatterns/ObserverPattern/ObserverPattern.razor

@@ -0,0 +1,40 @@
+@page "/Learn/DesignPatterns/ObserverPattern"
+
+@using MadWorld.Frontend.Application.DesignPatterns.ObserverPattern
+
+<div class="container">
+  <div class="row">
+    <div class="col-2">
+      <button class="btn btn-success" @onclick="() => ChangeFlag(RacingFlag.Green)">Show green flag</button>
+    </div>
+    <div class="col-2">
+      <button class="btn btn-warning" @onclick="() => ChangeFlag(RacingFlag.Yellow)">Show yellow flag</button>
+    </div>
+    <div class="col-2">
+      <button class="btn btn-danger" @onclick="() => ChangeFlag(RacingFlag.Red)">Show red flag</button>
+    </div>
+  </div>
+  <div class="row">
+    <div class="col-2">
+      <button class="btn btn-primary" @onclick="AddRedBull">Add Red Bull</button>
+    </div>
+    <div class="col-2">
+      <button class="btn btn-primary" @onclick="AddMercedes">Add Mercedes</button>
+    </div>
+  </div>
+  <div class="row">
+    @foreach (var car in _formulaOneCars)
+    {
+      <div class="col-4">
+        <div class="card" style="width: 18rem;">
+          <div class="card-body">
+            <h5 class="card-title">@car.Name</h5>
+            <p class="card-text">Speed: @car.GetRacingPace()</p>
+            <button class="btn btn-danger" @onclick="() => RemoveCar(car)">Remove @car.Name</button>
+          </div>
+        </div>
+      </div>
+    }
+  </div>
+</div>
+

MadWorld/MadWorld.Frontend.UI.Suite/Pages/Learn/DesignPatterns/ObserverPattern/ObserverPattern.razor.cs

@@ -0,0 +1,32 @@
+using JetBrains.Annotations;
+using MadWorld.Frontend.Application.DesignPatterns.ObserverPattern;
+
+namespace MadWorld.Frontend.UI.Suite.Pages.Learn.DesignPatterns.ObserverPattern;
+
+[UsedImplicitly]
+public partial class ObserverPattern
+{
+    private readonly FormulaOne _formulaOne = new();
+    private readonly List<ICar> _formulaOneCars = new();
+
+    private void ChangeFlag(RacingFlag flag)
+    {
+        _formulaOne.SetRacingFlag(flag);
+    }
+
+    private void AddRedBull()
+    {
+        _formulaOneCars.Add(new RedBull(_formulaOne));
+    }
+
+    private void AddMercedes()
+    {
+        _formulaOneCars.Add(new Mercedes(_formulaOne));
+    }
+
+    private void RemoveCar(ICar car)
+    {
+        _formulaOneCars.Remove(car);
+        car.Dispose();
+    }
+}

MadWorld/MadWorld.Frontend.UI.Suite/Pages/Learn/Learn.razor

@@ -0,0 +1,3 @@
+@page "/Learn"
+
+<a href="/Learn/DesignPatterns" class="btn btn-primary">Design Patterns</a>

MadWorld/MadWorld.Frontend.UI.Suite/Shared/NavMenu.razor

@@ -22,6 +22,11 @@
                 <span class="oi oi-clipboard" aria-hidden="true"></span> Curriculum Vitae
             </NavLink>
         </div>
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="/Learn">
+                <span class="oi oi-eye" aria-hidden="true"></span> Learn
+            </NavLink>
+        </div>
     </nav>
 </div>