Fix Blazor ViewModelActivation (#3871)

tomasfil · web-flow · commit 8729191f1f41 · 2024-08-02T18:19:32.000+02:00
**What kind of change does this PR introduce?**  Bug fix. Current implementation did increase RefCount under ViewModelActivator once, but decrement it twice on deactivation. So the ViewModel was bricked if it was used as Scoped, or Singleton and would never activate again. **What is the current behavior?**  Fixed behavior **What is the new behavior?**  **What might this PR break?** Should only fix **Please check if the PR fulfills these requirements** - [ ] Tests for the changes have been added (for bug fixes / features) - [ ] Docs have been added / updated (for bug fixes / features) **Other information**:
diff --git a/src/ReactiveUI.Blazor/ReactiveComponentBase.cs b/src/ReactiveUI.Blazor/ReactiveComponentBase.cs
@@ -69,6 +69,12 @@ public void Dispose()
     /// <inheritdoc />
     protected override void OnInitialized()
     {
+        if (ViewModel is IActivatableViewModel avm)
+        {
+            Activated.Subscribe(_ => avm.Activator.Activate()).DisposeWith(_compositeDisposable);
+            Deactivated.Subscribe(_ => avm.Activator.Deactivate());
+        }
+
         _initSubject.OnNext(Unit.Default);
         base.OnInitialized();
     }
diff --git a/src/ReactiveUI.Blazor/ReactiveInjectableComponentBase.cs b/src/ReactiveUI.Blazor/ReactiveInjectableComponentBase.cs
@@ -69,13 +69,14 @@ public void Dispose()
     /// <inheritdoc />
     protected override void OnInitialized()
     {
-        _initSubject.OnNext(Unit.Default);
         if (ViewModel is IActivatableViewModel avm)
         {
             Activated.Subscribe(_ => avm.Activator.Activate()).DisposeWith(_compositeDisposable);
             Deactivated.Subscribe(_ => avm.Activator.Deactivate());
         }
 
+        _initSubject.OnNext(Unit.Default);
+
         base.OnInitialized();
     }
 
diff --git a/src/ReactiveUI.Blazor/ReactiveLayoutComponentBase.cs b/src/ReactiveUI.Blazor/ReactiveLayoutComponentBase.cs
@@ -16,6 +16,9 @@ public class ReactiveLayoutComponentBase<T> : LayoutComponentBase, IViewFor<T>,
     where T : class, INotifyPropertyChanged
 {
     private readonly Subject<Unit> _initSubject = new();
+    [SuppressMessage("Design", "CA2213: Dispose object", Justification = "Used for deactivation.")]
+    private readonly Subject<Unit> _deactivateSubject = new();
+    private readonly CompositeDisposable _compositeDisposable = [];
 
     private T? _viewModel;
 
@@ -51,7 +54,7 @@ public T? ViewModel
     public IObservable<Unit> Activated => _initSubject.AsObservable();
 
     /// <inheritdoc />
-    public IObservable<Unit> Deactivated => Observable.Empty<Unit>();
+    public IObservable<Unit> Deactivated => _deactivateSubject.AsObservable();
 
     /// <inheritdoc />
     public void Dispose()
@@ -64,6 +67,12 @@ public void Dispose()
     /// <inheritdoc />
     protected override void OnInitialized()
     {
+        if (ViewModel is IActivatableViewModel avm)
+        {
+            Activated.Subscribe(_ => avm.Activator.Activate()).DisposeWith(_compositeDisposable);
+            Deactivated.Subscribe(_ => avm.Activator.Deactivate());
+        }
+
         _initSubject.OnNext(Unit.Default);
         base.OnInitialized();
     }
@@ -78,7 +87,8 @@ protected override void OnAfterRender(bool isFirstRender)
             this.WhenAnyValue(x => x.ViewModel)
                 .Skip(1)
                 .WhereNotNull()
-                .Subscribe(_ => InvokeAsync(StateHasChanged));
+                .Subscribe(_ => InvokeAsync(StateHasChanged))
+                .DisposeWith(_compositeDisposable);
         }
 
         this.WhenAnyValue(x => x.ViewModel)
@@ -93,7 +103,8 @@ protected override void OnAfterRender(bool isFirstRender)
                      eh => x.PropertyChanged -= eh))
             .Switch()
             .Do(_ => InvokeAsync(StateHasChanged))
-            .Subscribe();
+            .Subscribe()
+            .DisposeWith(_compositeDisposable);
     }
 
     /// <summary>
@@ -113,6 +124,8 @@ protected virtual void Dispose(bool disposing)
             if (disposing)
             {
                 _initSubject.Dispose();
+                _compositeDisposable.Dispose();
+                _deactivateSubject.OnNext(Unit.Default);
             }
 
             _disposedValue = true;

Original file line number	Diff line number	Diff line change
`@@ -69,6 +69,12 @@ public void Dispose()`
`69`	`69`	`/// <inheritdoc />`
`70`	`70`	`protected override void OnInitialized()`
`71`	`71`	`{`
	`72`	`+ if (ViewModel is IActivatableViewModel avm)`
	`73`	`+ {`
	`74`	`+ Activated.Subscribe(_ => avm.Activator.Activate()).DisposeWith(_compositeDisposable);`
	`75`	`+ Deactivated.Subscribe(_ => avm.Activator.Deactivate());`
	`76`	`+ }`
	`77`	`+`
`72`	`78`	`_initSubject.OnNext(Unit.Default);`
`73`	`79`	`base.OnInitialized();`
`74`	`80`	`}`
Original file line number	Diff line number	Diff line change
`@@ -69,13 +69,14 @@ public void Dispose()`
`69`	`69`	`/// <inheritdoc />`
`70`	`70`	`protected override void OnInitialized()`
`71`	`71`	`{`
`72`		`- _initSubject.OnNext(Unit.Default);`
`73`	`72`	`if (ViewModel is IActivatableViewModel avm)`
`74`	`73`	`{`
`75`	`74`	`Activated.Subscribe(_ => avm.Activator.Activate()).DisposeWith(_compositeDisposable);`
`76`	`75`	`Deactivated.Subscribe(_ => avm.Activator.Deactivate());`
`77`	`76`	`}`
`78`	`77`
	`78`	`+ _initSubject.OnNext(Unit.Default);`
	`79`	`+`
`79`	`80`	`base.OnInitialized();`
`80`	`81`	`}`
`81`	`82`