Merge pull request #4917 from worldbeater/sync-vm-and-datacontext

rxui: TwoWay DataContext and ViewModel Synchronization

src/Avalonia.ReactiveUI/ReactiveUserControl.cs

@@ -1,3 +1,6 @@
+using System;
+using System.Reactive.Disposables;
+using System.Reactive.Linq;
 using Avalonia;
 using Avalonia.VisualTree;
 using Avalonia.Controls;
@@ -6,8 +9,10 @@ using ReactiveUI;
 namespace Avalonia.ReactiveUI
 {
     /// <summary>
-    /// A ReactiveUI UserControl that implements <see cref="IViewFor{TViewModel}"/> 
-    /// and will activate your ViewModel automatically if it supports activation.
+    /// A ReactiveUI <see cref="UserControl"/> that implements the <see cref="IViewFor{TViewModel}"/> interface and
+    /// will activate your ViewModel automatically if the view model implements <see cref="IActivatableViewModel"/>.
+    /// When the DataContext property changes, this class will update the ViewModel property with the new DataContext
+    /// value, and vice versa.
     /// </summary>
     /// <typeparam name="TViewModel">ViewModel type.</typeparam>
     public class ReactiveUserControl<TViewModel> : UserControl, IViewFor<TViewModel> where TViewModel : class
@@ -20,7 +25,14 @@ namespace Avalonia.ReactiveUI
         /// </summary>
         public ReactiveUserControl()
         {
-            DataContextChanged += (sender, args) => ViewModel = DataContext as TViewModel;
+            // This WhenActivated block calls ViewModel's WhenActivated
+            // block if the ViewModel implements IActivatableViewModel.
+            this.WhenActivated(disposables => { });
+
+            this.ObservableForProperty(x => x.ViewModel, false, true)
+                .Subscribe(args => DataContext = args.Value);
+            this.ObservableForProperty(x => x.DataContext, false, true)
+                .Subscribe(args => ViewModel = args.Value as TViewModel);
         }
 
         /// <summary>

src/Avalonia.ReactiveUI/ReactiveWindow.cs

@@ -1,3 +1,6 @@
+using System;
+using System.Reactive.Disposables;
+using System.Reactive.Linq;
 using Avalonia;
 using Avalonia.VisualTree;
 using Avalonia.Controls;
@@ -6,8 +9,10 @@ using ReactiveUI;
 namespace Avalonia.ReactiveUI
 {
     /// <summary>
-    /// A ReactiveUI Window that implements <see cref="IViewFor{TViewModel}"/>
-    /// and will activate your ViewModel automatically if it supports activation.
+    /// A ReactiveUI <see cref="Window"/> that implements the <see cref="IViewFor{TViewModel}"/> interface and will
+    /// activate your ViewModel automatically if the view model implements <see cref="IActivatableViewModel"/>. When
+    /// the DataContext property changes, this class will update the ViewModel property with the new DataContext value,
+    /// and vice versa.
     /// </summary>
     /// <typeparam name="TViewModel">ViewModel type.</typeparam>
     public class ReactiveWindow<TViewModel> : Window, IViewFor<TViewModel> where TViewModel : class
@@ -20,7 +25,14 @@ namespace Avalonia.ReactiveUI
         /// </summary>
         public ReactiveWindow()
         {
-            DataContextChanged += (sender, args) => ViewModel = DataContext as TViewModel;
+            // This WhenActivated block calls ViewModel's WhenActivated
+            // block if the ViewModel implements IActivatableViewModel.
+            this.WhenActivated(disposables => { });
+
+            this.ObservableForProperty(x => x.ViewModel, false, true)
+                .Subscribe(args => DataContext = args.Value);
+            this.ObservableForProperty(x => x.DataContext, false, true)
+                .Subscribe(args => ViewModel = args.Value as TViewModel);
         }
             
         /// <summary>

tests/Avalonia.ReactiveUI.UnitTests/AvaloniaActivationForViewFetcherTest.cs

@@ -74,44 +74,26 @@ namespace Avalonia.ReactiveUI.UnitTests
         {
             public ActivatableWindow()
             {
-                InitializeComponent();
-                Assert.IsType<Border>(Content);
+                Content = new Border();
                 this.WhenActivated(disposables => { });
             }
-
-            private void InitializeComponent()
-            {
-                AvaloniaRuntimeXamlLoader.Load(@"
-<Window xmlns='https://github.com/avaloniaui'>
-    <Border/>
-</Window>", null, this);
-            }
         }
 
         public class ActivatableUserControl : ReactiveUserControl<ActivatableViewModel>
         {
             public ActivatableUserControl()
             {
-                InitializeComponent();
-                Assert.IsType<Border>(Content);
+                Content = new Border();
                 this.WhenActivated(disposables => { });
             }
-
-            private void InitializeComponent()
-            {
-                AvaloniaRuntimeXamlLoader.Load(@"
-<UserControl xmlns='https://github.com/avaloniaui'>
-    <Border/>
-</UserControl>", null, this);
-            }
         }
 
-        public AvaloniaActivationForViewFetcherTest()
-        {
-            Locator.CurrentMutable.RegisterConstant(
-                new AvaloniaActivationForViewFetcher(), 
-                typeof(IActivationForViewFetcher));
-        }
+        public AvaloniaActivationForViewFetcherTest() =>
+            Locator
+                .CurrentMutable
+                .RegisterConstant(
+                    new AvaloniaActivationForViewFetcher(),
+                    typeof(IActivationForViewFetcher));
 
         [Fact]
         public void Visual_Element_Is_Activated_And_Deactivated()

tests/Avalonia.ReactiveUI.UnitTests/ReactiveUserControlTest.cs

@@ -1,4 +1,4 @@
-using Avalonia.Controls;
+using System.Reactive.Disposables;
 using Avalonia.UnitTests;
 using ReactiveUI;
 using Splat;
@@ -8,14 +8,37 @@ namespace Avalonia.ReactiveUI.UnitTests
 {
     public class ReactiveUserControlTest
     {
-        public class ExampleViewModel : ReactiveObject { }
+        public class ExampleViewModel : ReactiveObject, IActivatableViewModel
+        {
+            public bool IsActive { get; private set; }
+
+            public ViewModelActivator Activator { get; } = new ViewModelActivator();
+
+            public ExampleViewModel() => this.WhenActivated(disposables =>
+            {
+                IsActive = true;
+                Disposable
+                    .Create(() => IsActive = false)
+                    .DisposeWith(disposables);
+            });
+        }
 
         public class ExampleView : ReactiveUserControl<ExampleViewModel> { }
 
+        public ReactiveUserControlTest() =>
+            Locator
+                .CurrentMutable
+                .RegisterConstant(
+                    new AvaloniaActivationForViewFetcher(),
+                    typeof(IActivationForViewFetcher));
+
         [Fact]
         public void Data_Context_Should_Stay_In_Sync_With_Reactive_User_Control_View_Model() 
         {
+            var root = new TestRoot();
             var view = new ExampleView();
+            root.Child = view;
+
             var viewModel = new ExampleViewModel();
             Assert.Null(view.ViewModel);
 
@@ -26,6 +49,56 @@ namespace Avalonia.ReactiveUI.UnitTests
             view.DataContext = null;
             Assert.Null(view.ViewModel);
             Assert.Null(view.DataContext);
+
+            view.ViewModel = viewModel;
+            Assert.Equal(viewModel, view.ViewModel);
+            Assert.Equal(viewModel, view.DataContext);
+
+            view.ViewModel = null;
+            Assert.Null(view.ViewModel);
+            Assert.Null(view.DataContext);
+        }
+
+        [Fact]
+        public void Should_Start_With_NotNull_Activated_ViewModel()
+        {
+            var root = new TestRoot();
+            var view = new ExampleView {ViewModel = new ExampleViewModel()};
+
+            Assert.False(view.ViewModel.IsActive);
+
+            root.Child = view;
+
+            Assert.NotNull(view.ViewModel);
+            Assert.NotNull(view.DataContext);
+            Assert.True(view.ViewModel.IsActive);
+
+            root.Child = null;
+
+            Assert.NotNull(view.ViewModel);
+            Assert.NotNull(view.DataContext);
+            Assert.False(view.ViewModel.IsActive);
+        }
+
+        [Fact]
+        public void Should_Start_With_NotNull_Activated_DataContext()
+        {
+            var root = new TestRoot();
+            var view = new ExampleView {DataContext = new ExampleViewModel()};
+
+            Assert.False(view.ViewModel.IsActive);
+
+            root.Child = view;
+
+            Assert.NotNull(view.ViewModel);
+            Assert.NotNull(view.DataContext);
+            Assert.True(view.ViewModel.IsActive);
+
+            root.Child = null;
+
+            Assert.NotNull(view.ViewModel);
+            Assert.NotNull(view.DataContext);
+            Assert.False(view.ViewModel.IsActive);
         }
     }
-}
+}

tests/Avalonia.ReactiveUI.UnitTests/ReactiveWindowTest.cs

@@ -1,4 +1,4 @@
-using Avalonia.Controls;
+using System.Reactive.Disposables;
 using Avalonia.UnitTests;
 using ReactiveUI;
 using Splat;
@@ -8,10 +8,30 @@ namespace Avalonia.ReactiveUI.UnitTests
 {
     public class ReactiveWindowTest
     {
-        public class ExampleViewModel : ReactiveObject { }
+        public class ExampleViewModel : ReactiveObject, IActivatableViewModel
+        {
+            public bool IsActive { get; private set; }
+
+            public ViewModelActivator Activator { get; } = new ViewModelActivator();
+
+            public ExampleViewModel() => this.WhenActivated(disposables =>
+            {
+                IsActive = true;
+                Disposable
+                    .Create(() => IsActive = false)
+                    .DisposeWith(disposables);
+            });
+        }
 
         public class ExampleWindow : ReactiveWindow<ExampleViewModel> { }
 
+        public ReactiveWindowTest() =>
+            Locator
+                .CurrentMutable
+                .RegisterConstant(
+                    new AvaloniaActivationForViewFetcher(),
+                    typeof(IActivationForViewFetcher));
+
         [Fact]
         public void Data_Context_Should_Stay_In_Sync_With_Reactive_Window_View_Model() 
         {
@@ -19,16 +39,73 @@ namespace Avalonia.ReactiveUI.UnitTests
             {
                 var view = new ExampleWindow();
                 var viewModel = new ExampleViewModel();
+                view.Show();
+
                 Assert.Null(view.ViewModel);
+                Assert.Null(view.DataContext);
 
                 view.DataContext = viewModel;
-                Assert.Equal(view.ViewModel, viewModel);
-                Assert.Equal(view.DataContext, viewModel);
+                Assert.Equal(viewModel, view.ViewModel);
+                Assert.Equal(viewModel, view.DataContext);
 
                 view.DataContext = null;
                 Assert.Null(view.ViewModel);
                 Assert.Null(view.DataContext);
+
+                view.ViewModel = viewModel;
+                Assert.Equal(viewModel, view.ViewModel);
+                Assert.Equal(viewModel, view.DataContext);
+
+                view.ViewModel = null;
+                Assert.Null(view.ViewModel);
+                Assert.Null(view.DataContext);
+            }
+        }
+
+        [Fact]
+        public void Should_Start_With_NotNull_Activated_ViewModel()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var view = new ExampleWindow { ViewModel = new ExampleViewModel() };
+
+                Assert.False(view.ViewModel.IsActive);
+
+                view.Show();
+
+                Assert.NotNull(view.ViewModel);
+                Assert.NotNull(view.DataContext);
+                Assert.True(view.ViewModel.IsActive);
+
+                view.Close();
+
+                Assert.NotNull(view.ViewModel);
+                Assert.NotNull(view.DataContext);
+                Assert.False(view.ViewModel.IsActive);
+            }
+        }
+
+        [Fact]
+        public void Should_Start_With_NotNull_Activated_DataContext()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var view = new ExampleWindow { DataContext = new ExampleViewModel() };
+
+                Assert.False(view.ViewModel.IsActive);
+
+                view.Show();
+
+                Assert.NotNull(view.ViewModel);
+                Assert.NotNull(view.DataContext);
+                Assert.True(view.ViewModel.IsActive);
+
+                view.Close();
+
+                Assert.NotNull(view.ViewModel);
+                Assert.NotNull(view.DataContext);
+                Assert.False(view.ViewModel.IsActive);
             }
         }
     }
-}
+}