IStateSelector<TState, TValue> #221 (#238)

Docs/disposable-callback-not-disposed.md

@@ -1,7 +1,7 @@
 # DisposableCallback was not disposed
 
 Components that descend from `FluxorComponent` or `FluxorLayout` automatically subscribe to the
-`StateChanged` event on every `IState<T>` property in the component automatically. When the component
+`StateChanged` event on every `IState<TState>` and `IStateSelection<TState, TValue>` property in the component automatically. When the component
 is disposed, this subscription is removed, to avoid memory leaks.
 
 If ever you see an error message like the following

Docs/releases.md

@@ -3,6 +3,7 @@
 ## New in 5.0
  * Removed need to reference `_content/Fluxor.Blazor.Web/scripts/index.js` ([#235](https://github.com/mrpmorris/Fluxor/issues/235))
  * Separated `IDispatcher` out of `IStore`. ([#209](https://github.com/mrpmorris/Fluxor/issues/209))
+ * Added `IState<TState>` alternative `IStateSelector<TState, TValue>` for selecting and subscribing to subsets of state. ([#221](https://github.com/mrpmorris/Fluxor/issues/221))
 
 ## New in 4.2.1
  * Support .NET 6

Source/Directory.Build.props

@@ -19,10 +19,11 @@
 		<SignAssembly>true</SignAssembly>
 		<DelaySign>false</DelaySign>
 		<GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+		<LangVersion>9</LangVersion>
 	</PropertyGroup>
 
 	<PropertyGroup>
-		<TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+		<TreatWarningsAsErrors>false</TreatWarningsAsErrors>
 		<NoWarn>NU5118</NoWarn>
 	</PropertyGroup>
 </Project>

Source/Fluxor.Blazor.Web.ReduxDevTools/Fluxor.Blazor.Web.ReduxDevTools.csproj

@@ -12,10 +12,6 @@
 
   </PropertyGroup>
 
-  <PropertyGroup>
-    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-  </PropertyGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Components" Version="3.1.8" />
     <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="3.1.8" />

Source/Fluxor.Blazor.Web/Components/FluxorComponent.cs

@@ -5,7 +5,7 @@
 namespace Fluxor.Blazor.Web.Components
 {
 	/// <summary>
-	/// A component that auto-subscribes to state changes on all <see cref="IState"/> properties
+	/// A component that auto-subscribes to state changes on all <see cref="IStateChangedNotifier"/> properties
 	/// and ensures <see cref="ComponentBase.StateHasChanged"/> is called
 	/// </summary>
 	public abstract class FluxorComponent : ComponentBase, IDisposable

Source/Fluxor.Blazor.Web/Components/FluxorLayout.cs

@@ -5,7 +5,7 @@
 namespace Fluxor.Blazor.Web.Components
 {
 	/// <summary>
-	/// A layout that auto-subscribes to state changes on all <see cref="IState"/> properties
+	/// A layout that auto-subscribes to state changes on all <see cref="IStateChangedNotifier"/> properties
 	/// and ensures <see cref="LayoutComponentBase.StateHasChanged"/> is called
 	/// </summary>
 	public abstract class FluxorLayout : LayoutComponentBase, IDisposable

Source/Fluxor.Blazor.Web/Middlewares/Routing/Effects.cs

@@ -14,7 +14,7 @@ public Effects(NavigationManager navigationManager)
 		}
 
 		[EffectMethod]
-		public Task HandleGoActionAsync(GoAction action, IDispatcher dispatcher)
+		public Task HandleGoActionAsync(GoAction action, IDispatcher _)
 		{
 			Uri fullUri = NavigationManager.ToAbsoluteUri(action.NewUri);
 			if (fullUri.ToString() != NavigationManager.Uri || action.ForceLoad)

Source/Fluxor.Blazor.Web/StoreInitializer.cs

@@ -99,23 +99,23 @@ protected virtual void Dispose(bool disposing)
 				Store.UnhandledException -= OnUnhandledException;
 		}
 
-		private void OnUnhandledException(object sender, Exceptions.UnhandledExceptionEventArgs args)
+		private void OnUnhandledException(object sender, Exceptions.UnhandledExceptionEventArgs e)
 		{
 			InvokeAsync(async () =>
 			{
 				Exception exceptionThrownInHandler = null;
 				try
 				{
-					await UnhandledException.InvokeAsync(args).ConfigureAwait(false);
+					await UnhandledException.InvokeAsync(e).ConfigureAwait(false);
 				}
-				catch (Exception e)
+				catch (Exception exception)
 				{
-					exceptionThrownInHandler = e;
+					exceptionThrownInHandler = exception;
 				}
 
-				if (exceptionThrownInHandler != null || !args.WasHandled)
+				if (exceptionThrownInHandler != null || !e.WasHandled)
 				{
-					ExceptionToThrow = exceptionThrownInHandler ?? args.Exception;
+					ExceptionToThrow = exceptionThrownInHandler ?? e.Exception;
 					StateHasChanged();
 				}
 			});

Source/Fluxor/DependencyInjection/InfoFactories/EffectMethodInfoFactory.cs

@@ -1,5 +1,4 @@
 using Microsoft.Extensions.DependencyInjection;
-using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;

Source/Fluxor/DependencyInjection/ServiceCollectionExtensions.cs

@@ -43,6 +43,7 @@ public static IServiceCollection AddFluxor(
 				typesToScan: options.TypesToScan,
 				scanIncludeList: scanIncludeList);
 			services.AddScoped(typeof(IState<>), typeof(State<>));
+			services.AddScoped(typeof(IStateSelection<,>), typeof(StateSelection<,>));
 
 			return services;
 		}

Source/Fluxor/Feature.cs

@@ -34,10 +34,10 @@ public abstract class Feature<TState> : IFeature<TState>
 		/// <summary>
 		/// A list of reducers registered with this feature
 		/// </summary>
-		protected readonly List<IReducer<TState>> Reducers = new List<IReducer<TState>>();
+		protected readonly List<IReducer<TState>> Reducers = new();
 
 		private bool HasInitialState;
-		private SpinLock SpinLock = new SpinLock();
+		private SpinLock SpinLock = new();
 		private readonly ThrottledInvoker TriggerStateChangedCallbacksThrottler;
 
 		/// <summary>
@@ -48,34 +48,17 @@ public Feature()
 			TriggerStateChangedCallbacksThrottler = new ThrottledInvoker(TriggerStateChangedCallbacks);
 		}
 
-		private EventHandler untypedStateChanged;
-		event EventHandler IFeature.StateChanged
+		private EventHandler _stateChanged;
+		public event EventHandler StateChanged
 		{
 			add
 			{
-				SpinLock.ExecuteLocked(() => untypedStateChanged += value );
+				SpinLock.ExecuteLocked(() => _stateChanged += value );
 			}
 
 			remove
 			{
-				SpinLock.ExecuteLocked(() => untypedStateChanged -= value);
-			}
-		}
-
-		private EventHandler<TState> stateChanged;
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		public event EventHandler<TState> StateChanged
-		{
-			add
-			{
-				SpinLock.ExecuteLocked(() => stateChanged += value);
-			}
-
-			remove
-			{
-				SpinLock.ExecuteLocked(() => stateChanged -= value);
+				SpinLock.ExecuteLocked(() => _stateChanged -= value);
 			}
 		}
 
@@ -134,8 +117,7 @@ public virtual void ReceiveDispatchNotificationFromStore(object action)
 
 		private void TriggerStateChangedCallbacks()
 		{
-			stateChanged?.Invoke(this, State);
-			untypedStateChanged?.Invoke(this, EventArgs.Empty);
+			_stateChanged?.Invoke(this, EventArgs.Empty);
 		}
 	}
 }

Source/Fluxor/IFeature.cs

@@ -74,10 +74,5 @@ public interface IFeature<TState> : IFeature
 		/// <param name="reducer">The reducer instance</param>
 		/// <seealso cref="DependencyInjection.Options.UseDependencyInjection(System.Reflection.Assembly[])"/>
 		void AddReducer(IReducer<TState> reducer);
-
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		new event EventHandler<TState> StateChanged;
 	}
 }

Source/Fluxor/IState.cs

@@ -1,33 +1,15 @@
-using System;
-
-namespace Fluxor
+namespace Fluxor
 {
-	/// <summary>
-	/// An interface that is injected into Blazor Components / pages for accessing
-	/// the state of an <see cref="IFeature{TState}"/>
-	/// </summary>
-	public interface IState
-	{
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		event EventHandler StateChanged;
-	}
-
 	/// <summary>
 	/// An interface that is injected into Blazor Components / pages for accessing
 	/// the state of an <see cref="IFeature{TState}"/>
 	/// </summary>
 	/// <typeparam name="TState">The type of the state</typeparam>
-	public interface IState<TState> : IState
+	public interface IState<TState> : IStateChangedNotifier
 	{
 		/// <summary>
-		/// Returns the current state of the feature
+		/// Returns the value selected from the feature state
 		/// </summary>
 		TState Value { get; }
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		new event EventHandler<TState> StateChanged;
 	}
 }

Source/Fluxor/IStateSelection.cs

@@ -0,0 +1,26 @@
+using System;
+
+namespace Fluxor
+{
+	/// <summary>
+	/// An interface that is injected into Blazor Components / pages for accessing
+	/// the a subset of state of an <see cref="IFeature{TState}"/>
+	/// </summary>
+	/// <typeparam name="TState">The type of the state</typeparam>
+	/// <typeparam name="TValue">The type of the value selected from <see cref="TState"/></typeparam>
+	public interface IStateSelection<TState, TValue> : IState<TValue>
+	{
+		/// <summary>
+		/// Identifies the part of the feature state to select
+		/// </summary>
+		/// <param name="selector">Function to select a value from the feature state</param>
+		/// <param name="valueEquals">
+		///		Optional function used to check if two values are equal. 
+		///		Used to determine if an update to state needs
+		///		to trigger a <see cref="IStateChangedNotifier.StateChanged"/> event
+		/// </param>
+		void Select(
+			Func<TState, TValue> selector,
+			Func<TValue, TValue, bool> valueEquals = null);
+	}
+}

Source/Fluxor/IStateValueChangedNotifier.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Fluxor
+{
+	public interface IStateChangedNotifier
+	{
+		/// <summary>
+		/// Event that is executed whenever the observed value of the state changes
+		/// </summary>
+		event EventHandler StateChanged;
+	}
+}

Source/Fluxor/State.cs

@@ -1,44 +1,20 @@
-using System;
-
-namespace Fluxor
+namespace Fluxor
 {
 	/// <summary>
 	/// A class that is injected into Blazor components/pages that provides access
 	/// to an <see cref="IFeature{TState}"/> state.
 	/// </summary>
 	/// <typeparam name="TState"></typeparam>
-	public class State<TState> : IState<TState>
+	public class State<TState> : StateSelection<TState, TState>, IStateSelection<TState, TState>
 	{
-		private readonly IFeature<TState> Feature;
-
-		/// <summary>
-		/// Creates an instance of the state holder
-		/// </summary>
-		/// <param name="feature">The feature that contains the state</param>
-		public State(IFeature<TState> feature)
-		{
-			Feature = feature;
-		}
-
-		/// <see cref="IState{TState}.Value"/>
-		public TState Value => Feature.State;
-
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		public event EventHandler<TState> StateChanged
+		public State(IFeature<TState> feature) : base(feature)
 		{
-			add { Feature.StateChanged += value; }
-			remove { Feature.StateChanged -= value; }
+			Select(
+				x => x, // Select the state itself
+				valueEquals: DefaultObjectReferenceEquals); // Compare by object reference
 		}
 
-		/// <summary>
-		/// Event that is executed whenever the state changes
-		/// </summary>
-		event EventHandler IState.StateChanged
-		{
-			add { (Feature as IFeature).StateChanged += value; }
-			remove { (Feature as IFeature).StateChanged -= value; }
-		}
+		private static bool DefaultObjectReferenceEquals(TState x, TState y) =>
+			object.ReferenceEquals(x, y);
 	}
 }