Constructor injection for ViewModels

Author: denis-tsv

samples/MvvmSample.Core/ViewModels/AsyncRelayCommandPageViewModel.cs

@@ -4,12 +4,13 @@
 
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.Input;
+using MvvmSample.Core.Services;
 
 namespace MvvmSample.Core.ViewModels;
 
 public class AsyncRelayCommandPageViewModel : SamplePageViewModel
 {
-    public AsyncRelayCommandPageViewModel()
+    public AsyncRelayCommandPageViewModel(IFilesService filesService) : base(filesService)
     {
         DownloadTextCommand = new AsyncRelayCommand(DownloadTextAsync);
     }

samples/MvvmSample.Core/ViewModels/IocPageViewModel.cs

@@ -6,4 +6,7 @@ namespace MvvmSample.Core.ViewModels;
 
 public class IocPageViewModel : SamplePageViewModel
 {
+    public IocPageViewModel(IFilesService filesService) : base(filesService)
+    {
+    }
 }

samples/MvvmSample.Core/ViewModels/MessengerPageViewModel.cs

@@ -7,12 +7,13 @@
 using CommunityToolkit.Mvvm.Input;
 using CommunityToolkit.Mvvm.Messaging;
 using CommunityToolkit.Mvvm.Messaging.Messages;
+using MvvmSample.Core.Services;
 
 namespace MvvmSample.Core.ViewModels;
 
 public class MessengerPageViewModel : SamplePageViewModel
 {
-    public MessengerPageViewModel()
+    public MessengerPageViewModel(IFilesService filesService) : base(filesService)
     {
         RequestCurrentUsernameCommand = new RelayCommand(RequestCurrentUsername);
         ResetCurrentUsernameCommand = new RelayCommand(ResetCurrentUsername);

samples/MvvmSample.Core/ViewModels/ObservableObjectPageViewModel.cs

@@ -5,12 +5,13 @@
 using System.Threading.Tasks;
 using System.Windows.Input;
 using CommunityToolkit.Mvvm.Input;
+using MvvmSample.Core.Services;
 
 namespace MvvmSample.Core.ViewModels;
 
 public class ObservableObjectPageViewModel : SamplePageViewModel
 {
-    public ObservableObjectPageViewModel()
+    public ObservableObjectPageViewModel(IFilesService filesService) : base(filesService)
     {
         ReloadTaskCommand = new RelayCommand(ReloadTask);
     }

samples/MvvmSample.Core/ViewModels/RelayCommandPageViewModel.cs

@@ -4,12 +4,13 @@
 
 using System.Windows.Input;
 using CommunityToolkit.Mvvm.Input;
+using MvvmSample.Core.Services;
 
 namespace MvvmSample.Core.ViewModels;
 
 public class RelayCommandPageViewModel : SamplePageViewModel
 {
-    public RelayCommandPageViewModel()
+    public RelayCommandPageViewModel(IFilesService filesService) : base(filesService)
     {
         IncrementCounterCommand = new RelayCommand(IncrementCounter);
     }

samples/MvvmSample.Core/ViewModels/SamplePageViewModel.cs

@@ -7,7 +7,6 @@
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.ComponentModel;
-using CommunityToolkit.Mvvm.DependencyInjection;
 using CommunityToolkit.Mvvm.Input;
 using MvvmSample.Core.Helpers;
 using MvvmSample.Core.Services;
@@ -22,10 +21,12 @@ public class SamplePageViewModel : ObservableObject
     /// <summary>
     /// The <see cref="IFilesService"/> instance currently in use.
     /// </summary>
-    private readonly IFilesService FilesServices = Ioc.Default.GetRequiredService<IFilesService>();
+    private readonly IFilesService FilesServices;
 
-    public SamplePageViewModel()
+    public SamplePageViewModel(IFilesService filesService)
     {
+        FilesServices = filesService;
+
         LoadDocsCommand = new AsyncRelayCommand<string>(LoadDocsAsync);
     }
 

samples/MvvmSample.Core/ViewModels/Widgets/SubredditWidgetViewModel.cs

@@ -22,12 +22,12 @@ public sealed class SubredditWidgetViewModel : ObservableRecipient
     /// <summary>
     /// Gets the <see cref="IRedditService"/> instance to use.
     /// </summary>
-    private readonly IRedditService RedditService = Ioc.Default.GetRequiredService<IRedditService>();
+    private readonly IRedditService RedditService;
 
     /// <summary>
     /// Gets the <see cref="ISettingsService"/> instance to use.
     /// </summary>
-    private readonly ISettingsService SettingsService = Ioc.Default.GetRequiredService<ISettingsService>();
+    private readonly ISettingsService SettingsService;
 
     /// <summary>
     /// An <see cref="AsyncLock"/> instance to avoid concurrent requests.
@@ -37,8 +37,11 @@ public sealed class SubredditWidgetViewModel : ObservableRecipient
     /// <summary>
     /// Creates a new <see cref="SubredditWidgetViewModel"/> instance.
     /// </summary>
-    public SubredditWidgetViewModel()
+    public SubredditWidgetViewModel(IRedditService redditService, ISettingsService settingsService)
     {
+        RedditService = redditService;
+        SettingsService = settingsService;
+
         LoadPostsCommand = new AsyncRelayCommand(LoadPostsAsync);
 
         selectedSubreddit = SettingsService.GetValue<string>(nameof(SelectedSubreddit)) ?? Subreddits[0];

samples/MvvmSampleXF/MvvmSampleXF/App.xaml.cs

@@ -1,15 +1,11 @@
 using CommunityToolkit.Mvvm.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection;
 using MvvmSample.Core.Services;
+using MvvmSample.Core.ViewModels;
+using MvvmSample.Core.ViewModels.Widgets;
 using MvvmSampleXF.Services;
-using MvvmSampleXF.Views;
 using Refit;
-using System;
-using System.IO;
-using System.Linq;
-using System.Reflection;
 using Xamarin.Forms;
-using Xamarin.Forms.Xaml;
 
 namespace MvvmSampleXF
 {
@@ -27,9 +23,19 @@ public App()
                 _initialized = true;
                 Ioc.Default.ConfigureServices(
                     new ServiceCollection()
+                    //Services
                     .AddSingleton<IFilesService, FileService>()
                     .AddSingleton<ISettingsService, SettingsService>()
-                    .AddSingleton(RestService.For<IRedditService>("https://www.reddit.com/"))
+                    .AddSingleton(RestService.For<IRedditService>("https://www.reddit.com/"))
+                    //ViewModels
+                    .AddTransient<PostWidgetViewModel>()
+                    .AddTransient<SubredditWidgetViewModel>()
+                    .AddTransient<AsyncRelayCommandPageViewModel>()
+                    .AddTransient<IocPageViewModel>()
+                    .AddTransient<MessengerPageViewModel>()
+                    .AddTransient<ObservableObjectPageViewModel>()
+                    .AddTransient<RelayCommandPageViewModel>()
+                    .AddTransient<SamplePageViewModel>()
                     .BuildServiceProvider());
             }
 

samples/MvvmSampleXF/MvvmSampleXF/Views/AsyncRelayCommandPage.xaml

@@ -8,9 +8,6 @@
 			 x:Class="MvvmSampleXF.Views.AsyncRelayCommandPage"
 			 x:DataType="vm:AsyncRelayCommandPageViewModel"
 			 Title="Commands">
-	<ContentPage.BindingContext>
-		<vm:AsyncRelayCommandPageViewModel x:Name="ViewModel" />
-	</ContentPage.BindingContext>
 	<ContentPage.Resources>
 		<converters:TaskResultConverter x:Key="TaskResultConverter" />
 	</ContentPage.Resources>

samples/MvvmSampleXF/MvvmSampleXF/Views/AsyncRelayCommandPage.xaml.cs

@@ -1,8 +1,10 @@
-using System;
+using MvvmSample.Core.ViewModels;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using CommunityToolkit.Mvvm.DependencyInjection;
 
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
@@ -15,8 +17,14 @@ public partial class AsyncRelayCommandPage : ContentPage
         public AsyncRelayCommandPage()
         {
             InitializeComponent();
+
+            ViewModel = Ioc.Default.GetRequiredService<AsyncRelayCommandPageViewModel>();
+
+            BindingContext = ViewModel;
         }
 
+        public AsyncRelayCommandPageViewModel ViewModel { get; }
+
         protected override void OnAppearing()
         {
             base.OnAppearing();