56 lines
2.4 KiB
C#
56 lines
2.4 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System.Runtime.CompilerServices;
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namespace CommunityToolkit.Mvvm.Messaging.Internals;
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/// <summary>
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/// A dispatcher type that invokes a given <see cref="MessageHandler{TRecipient, TMessage}"/> callback.
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/// </summary>
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/// <remarks>
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/// This type is used to avoid type aliasing with <see cref="Unsafe.As{T}(object)"/> when the generic
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/// arguments are not known. Additionally, this is an abstract class and not an interface so that when
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/// <see cref="Invoke(object, object)"/> is called, virtual dispatch will be used instead of interface
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/// stub dispatch, which is much slower and with more indirections.
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/// </remarks>
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internal abstract class MessageHandlerDispatcher
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{
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/// <summary>
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/// Invokes the current callback on a target recipient, with a specified message.
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/// </summary>
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/// <param name="recipient">The target recipient for the message.</param>
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/// <param name="message">The message being broadcast.</param>
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public abstract void Invoke(object recipient, object message);
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/// <summary>
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/// A generic version of <see cref="MessageHandlerDispatcher"/>.
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/// </summary>
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/// <typeparam name="TRecipient">The type of recipient for the message.</typeparam>
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/// <typeparam name="TMessage">The type of message to receive.</typeparam>
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public sealed class For<TRecipient, TMessage> : MessageHandlerDispatcher
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where TRecipient : class
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where TMessage : class
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{
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/// <summary>
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/// The underlying <see cref="MessageHandler{TRecipient, TMessage}"/> callback to invoke.
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/// </summary>
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private readonly MessageHandler<TRecipient, TMessage> handler;
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/// <summary>
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/// Initializes a new instance of the <see cref="For{TRecipient, TMessage}"/> class.
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/// </summary>
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/// <param name="handler">The input <see cref="MessageHandler{TRecipient, TMessage}"/> instance.</param>
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public For(MessageHandler<TRecipient, TMessage> handler)
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{
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this.handler = handler;
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}
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/// <inheritdoc/>
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public override void Invoke(object recipient, object message)
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{
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this.handler(Unsafe.As<TRecipient>(recipient), Unsafe.As<TMessage>(message));
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}
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}
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} |