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ReactiveComponentBase.cs
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ReactiveComponentBase.cs
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// Copyright (c) 2023 .NET Foundation and Contributors. All rights reserved.
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for full license information.
using System.Runtime.CompilerServices;
using Microsoft.AspNetCore.Components;
namespace ReactiveUI.Blazor;
/// <summary>
/// A base component for handling property changes and updating the blazer view appropriately.
/// </summary>
/// <typeparam name="T">The type of view model. Must support INotifyPropertyChanged.</typeparam>
public class ReactiveComponentBase<T> : ComponentBase, IViewFor<T>, INotifyPropertyChanged, ICanActivate, IDisposable
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 = new();
private T? _viewModel;
private bool _disposedValue; // To detect redundant calls
/// <inheritdoc />
public event PropertyChangedEventHandler? PropertyChanged;
/// <inheritdoc />
[Parameter]
public T? ViewModel
{
get => _viewModel;
set
{
if (EqualityComparer<T?>.Default.Equals(_viewModel, value))
{
return;
}
_viewModel = value;
OnPropertyChanged();
}
}
/// <inheritdoc />
object? IViewFor.ViewModel
{
get => ViewModel;
set => ViewModel = (T?)value;
}
/// <inheritdoc />
public IObservable<Unit> Activated => _initSubject.AsObservable();
/// <inheritdoc />
public IObservable<Unit> Deactivated => _deactivateSubject.AsObservable();
/// <inheritdoc />
public void Dispose()
{
// Do not change this code. Put cleanup code in Dispose(bool disposing) below.
Dispose(true);
GC.SuppressFinalize(this);
}
/// <inheritdoc />
protected override void OnInitialized()
{
_initSubject.OnNext(Unit.Default);
base.OnInitialized();
}
/// <inheritdoc/>
protected override void OnAfterRender(bool firstRender)
{
if (firstRender)
{
// The following subscriptions are here because if they are done in OnInitialized, they conflict with certain JavaScript frameworks.
var viewModelChanged =
this.WhenAnyValue(x => x.ViewModel)
.WhereNotNull()
.Publish()
.RefCount(2);
viewModelChanged
.Subscribe(_ => InvokeAsync(StateHasChanged))
.DisposeWith(_compositeDisposable);
viewModelChanged
.Select(x =>
Observable
.FromEvent<PropertyChangedEventHandler?, Unit>(
eventHandler =>
{
void Handler(object? sender, PropertyChangedEventArgs e) => eventHandler(Unit.Default);
return Handler;
},
eh => x.PropertyChanged += eh,
eh => x.PropertyChanged -= eh))
.Switch()
.Subscribe(_ => InvokeAsync(StateHasChanged))
.DisposeWith(_compositeDisposable);
}
base.OnAfterRender(firstRender);
}
/// <summary>
/// Invokes the property changed event.
/// </summary>
/// <param name="propertyName">The name of the property.</param>
protected virtual void OnPropertyChanged([CallerMemberName]string? propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
/// <summary>
/// Cleans up the managed resources of the object.
/// </summary>
/// <param name="disposing">If it is getting called by the Dispose() method rather than a finalizer.</param>
protected virtual void Dispose(bool disposing)
{
if (!_disposedValue)
{
if (disposing)
{
_initSubject.Dispose();
_compositeDisposable.Dispose();
_deactivateSubject.OnNext(Unit.Default);
}
_disposedValue = true;
}
}
}