Implement ViewModelComponent (#437)

* Implement ViewModelComponent with unified logic for storing/restoring/cleaning view models

* Update interface of Forms'  implementation of DialogsService

* Add documentation for ViewModelComponent class

* Update storage naming

* Throw exception if component is re-initialized

Softeq.XToolkit.WhiteLabel.Droid/Dialogs/DialogFragmentBase.cs

@@ -17,7 +17,7 @@
 namespace Softeq.XToolkit.WhiteLabel.Droid.Dialogs
 {
     public abstract class DialogFragmentBase<TViewModel> : DialogFragment, IBindable, IDialogFragment
-        where TViewModel : IDialogViewModel
+        where TViewModel : class, IDialogViewModel
     {
         private readonly Lazy<IContextProvider> _contextProviderLazy = Dependencies.Container.Resolve<Lazy<IContextProvider>>();
 

Softeq.XToolkit.WhiteLabel.Droid/Dialogs/DroidFragmentDialogService.cs

@@ -56,21 +56,21 @@ public Task<string> ShowDialogAsync(ActionSheetDialogConfig config)
 
         public Task<TResult> ShowForViewModel<TViewModel, TResult>(
             IEnumerable<NavigationParameterModel>? parameters = null)
-            where TViewModel : IDialogViewModel
+            where TViewModel : class, IDialogViewModel
         {
             return ShowForViewModelAsync<TViewModel, TResult>(parameters).WaitUntilDismissed();
         }
 
         public Task ShowForViewModel<TViewModel>(
             IEnumerable<NavigationParameterModel>? parameters = null)
-            where TViewModel : IDialogViewModel
+            where TViewModel : class, IDialogViewModel
         {
             return ShowForViewModelAsync<TViewModel>(parameters).WaitUntilDismissed();
         }
 
         public async Task<IDialogResult> ShowForViewModelAsync<TViewModel>(
             IEnumerable<NavigationParameterModel>? parameters = null)
-            where TViewModel : IDialogViewModel
+            where TViewModel : class, IDialogViewModel
         {
             var viewModel = CreateViewModel<TViewModel>(parameters);
 
@@ -81,7 +81,7 @@ public async Task<IDialogResult> ShowForViewModelAsync<TViewModel>(
 
         public async Task<IDialogResult<TResult>> ShowForViewModelAsync<TViewModel, TResult>(
             IEnumerable<NavigationParameterModel>? parameters = null)
-            where TViewModel : IDialogViewModel
+            where TViewModel : class, IDialogViewModel
         {
             var viewModel = CreateViewModel<TViewModel>(parameters);
 
@@ -109,7 +109,7 @@ private TViewModel CreateViewModel<TViewModel>(
         }
 
         protected virtual Task<object> ShowDialogAsync<TViewModel>(TViewModel viewModel)
-            where TViewModel : IDialogViewModel
+            where TViewModel : class, IDialogViewModel
         {
             var dialogFragment = (DialogFragmentBase<TViewModel>) _viewLocator.GetView(viewModel, ViewType.DialogFragment);
             dialogFragment.Show();

Softeq.XToolkit.WhiteLabel.Droid/Internal/IInstanceStorage.cs

@@ -0,0 +1,46 @@
+// Developed by Softeq Development Corporation
+// http://www.softeq.com
+
+using System.Collections.Generic;
+
+namespace Softeq.XToolkit.WhiteLabel.Droid.Internal
+{
+    /// <summary>
+    ///     Defines the contract for a storage that stores instances of different classes.
+    /// </summary>
+    internal interface IInstanceStorage
+    {
+        /// <summary>
+        ///     Returns an existing <typeparamref name="T"/> instance from the store.
+        /// </summary>
+        /// <typeparam name="T">The type of the instance to get.</typeparam>
+        /// <param name="key">The instance unique key.</param>
+        /// <returns>Stored instance.</returns>
+        T Get<T>(string key) where T : class;
+
+        /// <summary>
+        ///     Adds a <typeparamref name="T"/> instance to the store by <paramref name="key"/>.
+        /// </summary>
+        /// <typeparam name="T">The type of the instance to add.</typeparam>
+        /// <param name="key">The instance unique key.</param>
+        /// <param name="viewModel">The instance to add.</param>
+        void Add<T>(string key, T viewModel) where T : class;
+
+        /// <summary>
+        ///     Removes an existing instance from the store by <paramref name="key"/>.
+        /// </summary>
+        /// <param name="key">The instance unique key.</param>
+        void Remove(string key);
+
+        /// <summary>
+        ///     Removes an existing instances from the store by <paramref name="keys"/>.
+        /// </summary>
+        /// <param name="keys">The collection of instance unique keys.</param>
+        void Remove(IEnumerable<string> keys);
+
+        /// <summary>
+        ///     Clears store.
+        /// </summary>
+        void Clear();
+    }
+}

Softeq.XToolkit.WhiteLabel.Droid/Internal/ViewModelCache.cs

@@ -2,56 +2,47 @@
 // http://www.softeq.com
 
 using System.Collections.Generic;
-using Softeq.XToolkit.WhiteLabel.Mvvm;
 
 namespace Softeq.XToolkit.WhiteLabel.Droid.Internal
 {
     internal static class ViewModelCache
     {
-        private static readonly Dictionary<string, Dictionary<string, IViewModelBase>> _cache;
-
-        static ViewModelCache()
-        {
-            _cache = new Dictionary<string, Dictionary<string, IViewModelBase>>();
-        }
+        private static readonly Dictionary<string, Dictionary<string, object>> _cache =
+            new Dictionary<string, Dictionary<string, object>>();
 
         internal static TViewModel? Get<TViewModel>(string containerId, string key)
-            where TViewModel : class, IViewModelBase
+            where TViewModel : class
         {
-            var container = _cache.GetValueOrDefault(containerId);
-
-            if (container != null)
+            if (_cache.TryGetValue(containerId, out var container))
             {
                 return (TViewModel) container.GetValueOrDefault(key);
             }
 
             return null;
         }
 
-        internal static void Add(string containerId, string key, IViewModelBase viewModel)
+        internal static void Add(string containerId, string key, object viewModel)
         {
             if (!_cache.ContainsKey(containerId))
             {
-                _cache[containerId] = new Dictionary<string, IViewModelBase>();
+                _cache[containerId] = new Dictionary<string, object>();
             }
 
             _cache[containerId][key] = viewModel;
         }
 
         internal static void Remove(string containerId, string key)
         {
-            if (_cache.ContainsKey(containerId))
+            if (_cache.TryGetValue(containerId, out var container))
             {
-                _cache[containerId].Remove(key);
+                container.Remove(key);
             }
         }
 
-        internal static void Remove(string containerId, IReadOnlyCollection<string> keys)
+        internal static void Remove(string containerId, IEnumerable<string> keys)
         {
-            if (_cache.ContainsKey(containerId))
+            if (_cache.TryGetValue(containerId, out var container))
             {
-                var container = _cache[containerId];
-
                 foreach (var key in keys)
                 {
                     container.Remove(key);

Softeq.XToolkit.WhiteLabel.Droid/Internal/ViewModelStoreFragment.cs → Softeq.XToolkit.WhiteLabel.Droid/Internal/ViewModelStorageFragment.cs

@@ -5,11 +5,10 @@
 using System.Collections.Generic;
 using Android.OS;
 using AndroidX.Fragment.App;
-using Softeq.XToolkit.WhiteLabel.Mvvm;
 
 namespace Softeq.XToolkit.WhiteLabel.Droid.Internal
 {
-    internal sealed class ViewModelStoreFragment : Fragment, IViewModelStore
+    internal sealed class ViewModelStorageFragment : Fragment, IInstanceStorage
     {
         private const string ViewModelStoreIdKey = "WL_ViewModelStoreId";
 
@@ -19,7 +18,7 @@ internal sealed class ViewModelStoreFragment : Fragment, IViewModelStore
 
         /// <inheritdoc />
         public TViewModel Get<TViewModel>(string fragmentName)
-            where TViewModel : class, IViewModelBase
+            where TViewModel : class
         {
             var viewModel = ViewModelCache.Get<TViewModel>(ViewModelStoreId, fragmentName);
 
@@ -34,7 +33,8 @@ public TViewModel Get<TViewModel>(string fragmentName)
         }
 
         /// <inheritdoc />
-        public void Add(string fragmentName, IViewModelBase viewModel)
+        public void Add<TViewModel>(string fragmentName, TViewModel viewModel)
+            where TViewModel : class
         {
             ViewModelCache.Add(ViewModelStoreId, fragmentName, viewModel);
         }
@@ -46,7 +46,7 @@ public void Remove(string fragmentName)
         }
 
         /// <inheritdoc />
-        public void Remove(IReadOnlyList<string> fragmentNames)
+        public void Remove(IEnumerable<string> fragmentNames)
         {
             ViewModelCache.Remove(ViewModelStoreId, fragmentNames);
         }
@@ -58,7 +58,7 @@ public void Clear()
         }
 
         /// <inheritdoc />
-        public override void OnCreate(Bundle savedInstanceState)
+        public override void OnCreate(Bundle? savedInstanceState)
         {
             base.OnCreate(savedInstanceState);
 

Softeq.XToolkit.WhiteLabel.Droid/Internal/ViewModelStore.cs

@@ -10,23 +10,23 @@ internal static class ViewModelStore
     {
         private const string ViewModelStoreTag = "WL_ViewModelStore";
 
-        internal static IViewModelStore Of(FragmentManager fragmentManager)
+        internal static IInstanceStorage Of(FragmentManager fragmentManager)
         {
             return Get(fragmentManager);
         }
 
-        private static IViewModelStore Get(FragmentManager fragmentManager)
+        private static IInstanceStorage Get(FragmentManager fragmentManager)
         {
             if (fragmentManager.IsDestroyed)
             {
                 throw new InvalidOperationException("View Model store has been destroyed");
             }
 
-            var viewModelStore = (ViewModelStoreFragment?) fragmentManager.FindFragmentByTag(ViewModelStoreTag);
+            var viewModelStore = (ViewModelStorageFragment?) fragmentManager.FindFragmentByTag(ViewModelStoreTag);
 
             if (viewModelStore == null)
             {
-                viewModelStore = new ViewModelStoreFragment();
+                viewModelStore = new ViewModelStorageFragment();
 
                 fragmentManager
                     .BeginTransaction()

Softeq.XToolkit.WhiteLabel.Droid/Navigation/DroidFrameNavigationService.cs

@@ -32,7 +32,7 @@ public DroidFrameNavigationService(
 
         protected FrameNavigationConfig? Config { get; private set; }
 
-        private IViewModelStore CurrentStore
+        private IInstanceStorage CurrentStore
         {
             get
             {

Softeq.XToolkit.WhiteLabel.Droid/Softeq.XToolkit.WhiteLabel.Droid.csproj

@@ -84,6 +84,7 @@
     <Compile Include="ViewComponents\IViewComponent.cs" />
     <Compile Include="ViewComponents\ToastContainerComponent.cs" />
     <Compile Include="ViewComponents\ToolbarComponent.cs" />
+    <Compile Include="ViewComponents\ViewModelComponent.cs" />
     <Compile Include="Views\BottomNavigationFragmentBase.cs" />
     <Compile Include="Navigation\StartActivityAttribute.cs" />
     <Compile Include="Navigation\IViewLocator.cs" />
@@ -102,8 +103,8 @@
     <Compile Include="Internal\ViewModelStore.cs" />
     <Compile Include="Internal\BackStack.cs" />
     <Compile Include="Internal\ViewModelCache.cs" />
-    <Compile Include="Internal\ViewModelStoreFragment.cs" />
-    <Compile Include="Internal\IViewModelStore.cs" />
+    <Compile Include="Internal\ViewModelStorageFragment.cs" />
+    <Compile Include="Internal\IInstanceStorage.cs" />
     <Compile Include="Views\ToolbarFragmentBase.cs" />
     <Compile Include="Navigation\BackPressedCallback.cs" />
     <Compile Include="Dialogs\IDialogFragment.cs" />