Merge pull request #20 from theunrepentantgeek/feature/viewmodel-subs…

…criptions

Add subscriptions to our view models

src/WordTutor.Core/AddVocabularyWordScreen.cs

@@ -4,7 +4,7 @@
 
 namespace WordTutor.Core
 {
-    public class AddVocabularyWordScreen : Screen
+    public class AddVocabularyWordScreen : Screen, IEquatable<AddVocabularyWordScreen>
     {
         /// <summary>
         /// Gets the spelling currently shown on screen
@@ -64,5 +64,36 @@ public AddVocabularyWordScreen WithPronunciation(string pronunciation)
             Pronunciation = pronunciation ?? original.Pronunciation;
             Phrase = phrase ?? original.Phrase;
         }
+
+        public override bool Equals(object other) => Equals(other as AddVocabularyWordScreen);
+
+        public override bool Equals(Screen other) => Equals(other as VocabularyBrowserScreen);
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return Spelling.GetHashCode() * 23
+                    + Pronunciation.GetHashCode() * 41
+                    + Phrase.GetHashCode() * 71;
+            }
+        }
+
+        public bool Equals(AddVocabularyWordScreen other)
+        {
+            if (other is null)
+            {
+                return false;
+            }
+
+            if (ReferenceEquals(this, other))
+            {
+                return true;
+            }
+
+            return string.Equals(Spelling, other.Spelling, StringComparison.Ordinal)
+                && string.Equals(Pronunciation, other.Pronunciation, StringComparison.Ordinal)
+                && string.Equals(Phrase, other.Phrase, StringComparison.Ordinal);
+        }
     }
 }

src/WordTutor.Core/Redux/IReduxStore.cs

@@ -23,8 +23,8 @@ public interface IReduxStore<T>
         /// <param name="whenChanged">Action to invoke when the value changes.</param>
         /// <returns>Subscription object; disposal release the subscription.</returns>
         IDisposable Subscribe<V>(
-            Func<T, V> reader, 
-            Action<V> whenChanged) 
-            where V : System.IEquatable<V>;
+            Func<T, V> reader,
+            Action<V> whenChanged)
+            where V : IEquatable<V>;
     }
 }

src/WordTutor.Core/Redux/ReduxStore.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace WordTutor.Core.Redux
 {
@@ -28,7 +29,7 @@ public class ReduxStore<T> : IReduxStore<T>
         /// <param name="reducer">Reducer to use for state transformations.</param>
         /// <param name="initialStateFactory">Factory used to create the initial state of the application.</param>
         public ReduxStore(
-            IReduxReducer<T> reducer, 
+            IReduxReducer<T> reducer,
             IReduxStateFactory<T> initialStateFactory)
         {
             _reducer = reducer ?? throw new ArgumentNullException(nameof(reducer));
@@ -61,7 +62,7 @@ public void Dispatch(IReduxMessage message)
                 _dispatching = false;
             }
 
-            foreach (var subscription in _subscriptions)
+            foreach (var subscription in _subscriptions.ToList())
             {
                 subscription.Publish(State);
             }
@@ -77,7 +78,7 @@ public void Dispatch(IReduxMessage message)
         public IDisposable Subscribe<V>(
             Func<T, V> reader,
             Action<V> whenChanged)
-            where V: IEquatable<V>
+            where V : IEquatable<V>
         {
             var subscription = new ReduxSubscription<T, V>(
                 reader ?? throw new ArgumentNullException(nameof(reader)),

src/WordTutor.Core/Screen.cs

@@ -1,8 +1,10 @@
-namespace WordTutor.Core
+using System;
+
+namespace WordTutor.Core
 {
-    public abstract class Screen
+    public abstract class Screen : IEquatable<Screen>
     {
-
+        public abstract bool Equals(Screen other);
     }
 
 }

src/WordTutor.Core/VocabularyBrowserScreen.cs

@@ -2,7 +2,7 @@
 
 namespace WordTutor.Core
 {
-    public class VocabularyBrowserScreen : Screen
+    public class VocabularyBrowserScreen : Screen, IEquatable<VocabularyBrowserScreen>
     {
         /// <summary>
         /// Gets the currently selected word
@@ -54,6 +54,35 @@ public VocabularyBrowserScreen MarkAsUnmodified()
                 modified: false);
         }
 
+        public override bool Equals(object obj) => Equals(obj as VocabularyBrowserScreen);
+
+        public override bool Equals(Screen other) => Equals(other as VocabularyBrowserScreen);
+
+        public bool Equals(VocabularyBrowserScreen other)
+        {
+            if (other is null)
+            {
+                return false;
+            }
+
+            if (ReferenceEquals(this, other))
+            {
+                return true;
+            }
+
+            return Selection.Equals(other.Selection)
+                && Modified == other.Modified;
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return Selection.GetHashCode() * 23
+                    + Modified.GetHashCode();
+            }
+        }
+
         private VocabularyBrowserScreen(
             VocabularyBrowserScreen original,
             VocabularyWord selection = null,

src/WordTutor.Desktop/AddVocabularyWordViewModel.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using WordTutor.Core;
 using WordTutor.Core.Actions;
 using WordTutor.Core.Redux;
@@ -8,6 +8,7 @@ namespace WordTutor.Desktop
     public class AddVocabularyWordViewModel : ViewModelBase
     {
         private readonly IReduxStore<WordTutorApplication> _store;
+        private readonly IDisposable _screenSubscription;
 
         private string _spelling;
         private string _phrase;
@@ -16,7 +17,15 @@ public class AddVocabularyWordViewModel : ViewModelBase
         public AddVocabularyWordViewModel(IReduxStore<WordTutorApplication> store)
         {
             _store = store ?? throw new ArgumentNullException(nameof(store));
-            UpdateFromStore();
+
+            var screen = _store.State.CurrentScreen as AddVocabularyWordScreen;
+            _spelling = screen?.Spelling ?? string.Empty;
+            _phrase = screen?.Phrase ?? string.Empty;
+            _pronunciation = screen?.Pronunciation ?? string.Empty;
+
+            _screenSubscription = _store.Subscribe(
+                app => app.CurrentScreen as AddVocabularyWordScreen,
+                RefreshFromScreen);
         }
 
         public string Spelling
@@ -46,16 +55,17 @@ public string Pronunciation
                 pr => _store.Dispatch(new ModifyPronunciationMessage(pr)));
         }
 
-        private void UpdateFromStore()
+        private void RefreshFromScreen(AddVocabularyWordScreen screen)
         {
-            var model = _store.State.CurrentScreen as AddVocabularyWordScreen;
-
-            if (!(model is null))
+            if (screen is null)
             {
-                Spelling = model?.Spelling ?? string.Empty;
-                Phrase = model?.Phrase ?? string.Empty;
-                Pronunciation = model?.Pronunciation ?? string.Empty;
+                _screenSubscription.Dispose();
+                return;
             }
+
+            Spelling = screen.Spelling ?? string.Empty;
+            Phrase = screen.Phrase ?? string.Empty;
+            Pronunciation = screen.Pronunciation ?? string.Empty;
         }
     }
 }

src/WordTutor.Desktop/VocabularyBrowserViewModel.cs

@@ -11,15 +11,31 @@ public class VocabularyBrowserViewModel : ViewModelBase
     {
         private readonly IReduxStore<WordTutorApplication> _store;
         private readonly ObservableCollection<VocabularyWord> _words;
+        private readonly IDisposable _screenSubscription;
+        private readonly IDisposable _vocabularySubscription;
 
         private VocabularyWord _selection;
         private bool _modified;
 
         public VocabularyBrowserViewModel(IReduxStore<WordTutorApplication> store)
         {
             _store = store ?? throw new ArgumentNullException(nameof(store));
-            _words = new ObservableCollection<VocabularyWord>();
-            RefreshFromApplication(_store.State);
+
+            var screen = (VocabularyBrowserScreen)_store.State.CurrentScreen;
+            var vocab = _store.State.VocabularySet.Words;
+
+            _selection = screen.Selection;
+            _modified = screen.Modified;
+            _words = new ObservableCollection<VocabularyWord>(
+                vocab.OrderBy(w => w.Spelling));
+
+            _screenSubscription = _store.Subscribe(
+                app => app.CurrentScreen as VocabularyBrowserScreen,
+                RefreshFromScreen);
+
+            _vocabularySubscription = _store.Subscribe(
+                app => app.VocabularySet,
+                RefreshFromVocabularySet);
         }
 
         public VocabularyWord Selection
@@ -42,22 +58,25 @@ public ObservableCollection<VocabularyWord> Words
             get => _words;
         }
 
-        private void RefreshFromApplication(WordTutorApplication application)
+        private void RefreshFromScreen(VocabularyBrowserScreen screen)
         {
-            var screen = application.CurrentScreen as VocabularyBrowserScreen;
-            if (!(screen is null))
+            if (screen == null)
             {
-                Selection = screen.Selection;
-                Modified = screen.Modified;
+                _screenSubscription.Dispose();
+                _vocabularySubscription.Dispose();
+                return;
             }
 
-            if (!(application.VocabularySet is null))
-            {
-                var words = application.VocabularySet.Words
-                    .OrderBy(w => w.Spelling)
-                    .ToList();
-                UpdateCollection(_words, words);
-            }
+            Selection = screen.Selection;
+            Modified = screen.Modified;
+        }
+
+        private void RefreshFromVocabularySet(VocabularySet vocabularySet)
+        {
+            var words = vocabularySet.Words
+                .OrderBy(w => w.Spelling)
+                .ToList();
+            UpdateCollection(_words, words);
         }
     }
 }

src/WordTutor.Desktop/WordTutorViewModel.cs

@@ -1,4 +1,5 @@
-using WordTutor.Core;
+using System;
+using WordTutor.Core;
 using WordTutor.Core.Redux;
 
 namespace WordTutor.Desktop
@@ -7,6 +8,7 @@ public class WordTutorViewModel : ViewModelBase
     {
         private readonly IReduxStore<WordTutorApplication> _store;
         private readonly ViewModelFactory _factory;
+        private readonly IDisposable _screenSubscription;
 
         private ViewModelBase _currentScreen;
 
@@ -16,8 +18,11 @@ public class WordTutorViewModel : ViewModelBase
         {
             _store = store;
             _factory = factory;
+            _currentScreen = _factory.Create(_store.State.CurrentScreen);
 
-            UpdateFromStore();
+            _screenSubscription = _store.Subscribe(
+                app => app.CurrentScreen,
+                RefreshFromScreen);
         }
 
         public ViewModelBase CurrentScreen
@@ -33,9 +38,17 @@ public ViewModelBase CurrentScreen
             }
         }
 
-        private void UpdateFromStore()
+        private void RefreshFromScreen(Screen screen)
         {
-            CurrentScreen = _factory.Create(_store.State.CurrentScreen);
+            // Only need a new instance if the screen type changes
+            // As long as the type of screen is unchanged, 
+            // the exiting ViewModel will update
+
+            var neededType = ViewModelFactory.FindViewModelType(screen.GetType());
+            if (CurrentScreen?.GetType() != neededType)
+            {
+                CurrentScreen = _factory.Create(screen);
+            }
         }
     }
 }

tests/WordTutor.Core.Tests/Fakes/FakeScreen.cs

@@ -1,13 +1,10 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace WordTutor.Core.Tests.Fakes
+namespace WordTutor.Core.Tests.Fakes
 {
     /// <summary>
     /// A fake screen for use when testing
     /// </summary>
     public class FakeScreen : Screen
     {
+        public override bool Equals(Screen other) => other is FakeScreen;
     }
 }