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

@@ -2,9 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using MvvmSample.Core.Services;
+
 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

@@ -6,7 +6,6 @@
 using System.IO;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.ComponentModel;
-using CommunityToolkit.Mvvm.DependencyInjection;
 using CommunityToolkit.Mvvm.Input;
 using MvvmSample.Core.Helpers;
 using MvvmSample.Core.Services;
@@ -21,10 +20,12 @@ 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.
@@ -37,11 +37,14 @@ 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];
+            selectedSubreddit = SettingsService.GetValue<string>(nameof(SelectedSubreddit)) ?? Subreddits[0];           
         }
 
         /// <summary>

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();