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glennawatson merged 4 commits into from
Jul 26, 2026
Merged

refactor: consolidate duplicated reactive plumbing #4418

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caa0ce4
refactor: consolidate duplicated reactive plumbing
glennawatson Jul 25, 2026
c386e50
chore: Add unit tests
glennawatson Jul 25, 2026
e1d3b90
refactor: close quality gate gaps
glennawatson Jul 26, 2026
1fff99c
Add more test scenarios
glennawatson Jul 26, 2026
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82 changes: 8 additions & 74 deletions src/ReactiveUI.Maui/Common/RoutedViewHost.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,11 @@
#if WINUI_TARGET
using System.Diagnostics.CodeAnalysis;
using Microsoft.UI.Xaml;
using ReactiveUI.Internal;
#if REACTIVE_SHIM
using ReactiveUI.Reactive.Maui.Internal;
#else
using ReactiveUI.Maui.Internal;
#endif
using ReactiveUI.Primitives;
using Splat;

#if REACTIVE_SHIM
Expand Down Expand Up @@ -58,78 +56,14 @@ public RoutedViewHost()
HorizontalContentAlignment = HorizontalAlignment.Stretch;
VerticalContentAlignment = VerticalAlignment.Stretch;

var platform = AppLocator.Current.GetService<IPlatformOperations>();
Func<string?> platformGetter = static () => default;

if (platform is null)
{
// NB: This used to be an error but WPF design mode can't read
// good or do other stuff good.
this.Log().Error(
"Couldn't find an IPlatformOperations implementation. Please make sure you have installed the latest "
+ "version of the ReactiveUI packages for your platform. See https://reactiveui.net/docs/getting-started/installation for guidance.");
}
else
{
platformGetter = platform.GetOrientation;
}

ViewContractObservable = ModeDetector.InUnitTestRunner()
? Signal.Silent<string>()

// Replaces FromEvent(SizeChanged).StartWith(platformGetter()).DistinctUntilChanged().
: new StartWithObservable<string?>(
new FromEventObservable<string?>(onNext =>
{
SizeChangedEventHandler handler = (_, _) => onNext(platformGetter());
SizeChanged += handler;
return new ActionDisposable(() => SizeChanged -= handler);
}),
platformGetter())
.DistinctUntilChanged();

// Observe Router property changes using DependencyProperty (AOT-friendly)
var routerChanged = MauiReactiveHelpers.CreatePropertyValueObservable(
this,
nameof(Router),
RouterProperty,
() => Router);

// Observe ViewContractObservable property changes using DependencyProperty (AOT-friendly)
var viewContractObservableChanged = MauiReactiveHelpers.CreatePropertyValueObservable(
this,
nameof(ViewContractObservable),
ViewContractObservableProperty,
() => ViewContractObservable);

// Observe current view model from router. Replaces Where(...).SelectMany(r => r.CurrentViewModel).StartWith(null).
var currentViewModel = new StartWithObservable<IRoutableViewModel?>(
new KeepSignal<RoutingState?>(routerChanged, static router => router is not null)
.SelectMany(static router => router!.CurrentViewModel),
null);

// Flatten the ViewContractObservable observable-of-observable.
// Replaces SelectMany(x => x ?? Return(null)).Do(x => _viewContract = x).StartWith(ViewContract).
var viewContract = new StartWithObservable<string?>(
viewContractObservableChanged
.SelectMany(static x => x ?? Signal.Emit<string?>(null))
.Do(x => _viewContract = x),
ViewContract);

var viewModelAndContract = currentViewModel
.CombineLatest(
viewContract,
static (viewModel, contract) => (viewModel, contract));

// Subscribe directly without WhenActivated
// NB: The DistinctUntilChanged is useful because most views in
// WinRT will end up getting here twice - once for configuring
// the RoutedViewHost's ViewModel, and once on load via SizeChanged
_ = viewModelAndContract.DistinctUntilChanged()
.Subscribe(new DelegateObserver<(IRoutableViewModel? viewModel, string? contract)>(
ResolveViewForViewModel,
RxState.DefaultExceptionHandler.OnNext))
.DisposeWith(_subscriptions);
MauiReactiveHelpers.InitializeRoutedViewHost(
(this, this.Log(), observable => ViewContractObservable = observable),
(nameof(Router), RouterProperty, () => Router),
(nameof(ViewContractObservable), ViewContractObservableProperty, () => ViewContractObservable),
() => ViewContract,
contract => _viewContract = contract,
ResolveViewForViewModel,
_subscriptions);
}

/// <summary>Gets or sets the <see cref="RoutingState"/> of the view model stack.</summary>
Expand Down
94 changes: 14 additions & 80 deletions src/ReactiveUI.Maui/Common/RoutedViewHost{TViewModel}.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,11 @@
#if WINUI_TARGET
using System.Diagnostics.CodeAnalysis;
using Microsoft.UI.Xaml;
using ReactiveUI.Internal;
#if REACTIVE_SHIM
using ReactiveUI.Reactive.Maui.Internal;
#else
using ReactiveUI.Maui.Internal;
#endif
using ReactiveUI.Primitives;
using Splat;

#if REACTIVE_SHIM
Expand Down Expand Up @@ -60,80 +58,22 @@ public RoutedViewHost()
HorizontalContentAlignment = HorizontalAlignment.Stretch;
VerticalContentAlignment = VerticalAlignment.Stretch;

var platform = AppLocator.Current.GetService<IPlatformOperations>();
Func<string?> platformGetter = static () => default;

if (platform is null)
{
// NB: This used to be an error but WPF design mode can't read
// good or do other stuff good.
this.Log().Error(
"Couldn't find an IPlatformOperations implementation. Please make sure you have installed the latest "
+ "version of the ReactiveUI packages for your platform. See https://reactiveui.net/docs/getting-started/installation for guidance.");
}
else
{
platformGetter = platform.GetOrientation;
}

ViewContractObservable = ModeDetector.InUnitTestRunner()
? Signal.Silent<string>()

// Replaces FromEvent(SizeChanged).StartWith(platformGetter()).DistinctUntilChanged().
: new StartWithObservable<string?>(
new FromEventObservable<string?>(onNext =>
{
SizeChangedEventHandler handler = (_, _) => onNext(platformGetter());
SizeChanged += handler;
return new ActionDisposable(() => SizeChanged -= handler);
}),
platformGetter())
.DistinctUntilChanged();

// Observe Router property changes using DependencyProperty (AOT-friendly)
var routerChanged = MauiReactiveHelpers.CreatePropertyValueObservable(
this,
nameof(Router),
RouterProperty,
() => Router);

// Observe ViewContractObservable property changes using DependencyProperty (AOT-friendly)
var viewContractObservableChanged = MauiReactiveHelpers.CreatePropertyValueObservable(
this,
nameof(ViewContractObservable),
ViewContractObservableProperty,
() => ViewContractObservable);

// Observe current view model from router. Replaces Where(...).SelectMany(r => r.CurrentViewModel).StartWith(null).
var currentViewModel = new StartWithObservable<IRoutableViewModel?>(
new KeepSignal<RoutingState?>(routerChanged, static router => router is not null)
.SelectMany(static router => router!.CurrentViewModel),
null);

// Flatten the ViewContractObservable observable-of-observable.
// Replaces SelectMany(x => x ?? Return(null)).Do(x => _viewContract = x).StartWith(ViewContract).
var viewContract = new StartWithObservable<string?>(
viewContractObservableChanged
.SelectMany(static x => x ?? Signal.Emit<string?>(null))
.Do(x => _viewContract = x),
ViewContract);

var viewModelAndContract = currentViewModel
.CombineLatest(
viewContract,
static (viewModel, contract) => (viewModel, contract));

// Subscribe directly without WhenActivated
// NB: The DistinctUntilChanged is useful because most views in
// WinRT will end up getting here twice - once for configuring
// the RoutedViewHost's ViewModel, and once on load via SizeChanged
_ = viewModelAndContract.DistinctUntilChanged()
.Subscribe(new DelegateObserver<(IRoutableViewModel? viewModel, string? contract)>(
ResolveViewForViewModel,
RxState.DefaultExceptionHandler.OnNext))
.DisposeWith(_subscriptions);
MauiReactiveHelpers.InitializeRoutedViewHost(
(this, this.Log(), observable => ViewContractObservable = observable),
(nameof(Router), RouterProperty, () => Router),
(nameof(ViewContractObservable), ViewContractObservableProperty, () => ViewContractObservable),
() => ViewContract,
contract => _viewContract = contract,
ResolveViewForViewModel,
_subscriptions);
}

/// <summary>Gets or sets the view locator.</summary>
/// <value>
/// The view locator.
/// </value>
public IViewLocator? ViewLocator { get; set; }

/// <summary>Gets or sets the <see cref="RoutingState"/> of the view model stack.</summary>
public RoutingState Router
{
Expand Down Expand Up @@ -169,12 +109,6 @@ public string? ViewContract
}
}

/// <summary>Gets or sets the view locator.</summary>
/// <value>
/// The view locator.
/// </value>
public IViewLocator? ViewLocator { get; set; }

/// <summary>
/// Resolves and displays the view for the given view model and contract.
/// This method uses the generic ViewLocator.ResolveView{TViewModel} which is AOT-safe.
Expand Down
60 changes: 6 additions & 54 deletions src/ReactiveUI.Maui/Common/ViewModelViewHost.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,13 +5,11 @@

using System.Diagnostics.CodeAnalysis;
using Microsoft.UI.Xaml;
using ReactiveUI.Internal;
#if REACTIVE_SHIM
using ReactiveUI.Reactive.Maui.Internal;
#else
using ReactiveUI.Maui.Internal;
#endif
using ReactiveUI.Primitives;
using Splat;

#if REACTIVE_SHIM
Expand Down Expand Up @@ -58,58 +56,12 @@ public partial class ViewModelViewHost : TransitioningContentControl, IViewFor,
Justification = "The single-threaded UI control hands 'this' to MauiReactiveHelpers to observe its own dependency-property changes; it is never published to another thread.")]
public ViewModelViewHost()
{
var platform = AppLocator.Current.GetService<IPlatformOperations>();
Func<string?> platformGetter = static () => default;

if (platform is null)
{
// NB: This used to be an error but WPF design mode can't read
// good or do other stuff good.
this.Log().Error(
"Couldn't find an IPlatformOperations implementation. Please make sure you have installed the latest "
+ "version of the ReactiveUI packages for your platform. See https://reactiveui.net/docs/getting-started/installation for guidance.");
}
else
{
platformGetter = platform.GetOrientation;
}

ViewContractObservable = ModeDetector.InUnitTestRunner()
? Signal.Silent<string>()

// Replaces FromEvent(SizeChanged).StartWith(platformGetter()).DistinctUntilChanged().
: new StartWithObservable<string?>(
new FromEventObservable<string?>(onNext =>
{
SizeChangedEventHandler handler = (_, _) => onNext(platformGetter());
SizeChanged += handler;
return new ActionDisposable(() => SizeChanged -= handler);
}),
platformGetter())
.DistinctUntilChanged();

// Observe ViewModel property changes without expression trees (AOT-friendly)
var viewModelChanged = MauiReactiveHelpers.CreatePropertyValueObservable(
this,
nameof(ViewModel),
ViewModelProperty,
() => ViewModel);

// Combine contract observable (recording the latest contract) with ViewModel changes.
var viewModelAndContract = ViewContractObservable.Do(x => _viewContract = x)
.CombineLatest(
viewModelChanged,
static (contract, vm) => (vm, contract));

// Subscribe directly without WhenActivated
_ = new ObserveOnObservable<string?>(ViewContractObservable, RxSchedulers.MainThreadScheduler)
.Subscribe(new DelegateObserver<string?>(x => _viewContract = x ?? string.Empty))
.DisposeWith(_subscriptions);

_ = viewModelAndContract.DistinctUntilChanged()
.Subscribe(new DelegateObserver<(object? ViewModel, string? Contract)>(
x => ResolveViewForViewModel(x.ViewModel, x.Contract)))
.DisposeWith(_subscriptions);
MauiReactiveHelpers.InitializeViewModelViewHost(
(this, this.Log(), observable => ViewContractObservable = observable),
(nameof(ViewModel), ViewModelProperty, () => ViewModel),
contract => _viewContract = contract,
ResolveViewForViewModel,
_subscriptions);
}

/// <summary>Gets or sets the view contract observable.</summary>
Expand Down
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