49 lines
2.5 KiB
Markdown
49 lines
2.5 KiB
Markdown
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---
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uid: Guides.IntFw.AutoCompletion
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title: Command Autocompletion
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---
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# AutocompleteHandlers
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[AutocompleteHandler]s provide a similar pattern to TypeConverters.
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[AutocompleteHandler]s are cached, singleton services and they are used by the
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Interaction Service to handle Autocomplete Interactions targeted to a specific Slash Command parameter.
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To start using AutocompleteHandlers, use the `[AutocompleteAttribute(Type type)]` overload of the [AutocompleteAttribute].
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This will dynamically link the parameter to the [AutocompleteHandler] type.
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AutocompleteHandlers raise the `AutocompleteHandlerExecuted` event on execution. This event can be also used to create a post-execution logic, just like the `*CommandExecuted` events.
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## Creating AutocompleteHandlers
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A valid AutocompleteHandlers must inherit [AutocompleteHandler] base type and implement all of its abstract methods.
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[!code-csharp[Autocomplete Command Example](samples/autocompletion/autocomplete-example.cs)]
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### GenerateSuggestionsAsync()
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The Interactions Service uses this method to generate a response of an Autocomplete Interaction.
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This method should return `AutocompletionResult.FromSuccess(IEnumerable<AutocompleteResult>)` to
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display parameter suggestions to the user. If there are no suggestions to be presented to the user, you have two results:
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1. Returning the parameterless `AutocompletionResult.FromSuccess()` will display a "No options match your search." message to the user.
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2. Returning `AutocompleteResult.FromError()` will make the Interaction Service **not** respond to the interaction,
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consequently displaying the user a "Loading options failed." message. `AutocompletionResult.FromError()` is solely used for error handling purposes. Discord currently doesn't allow
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you to display custom error messages. This result type will be directly returned to the `AutocompleteHandlerExecuted` method.
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## Resolving AutocompleteHandler Dependencies
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AutocompleteHandler dependencies are resolved using the same dependency injection
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pattern as the Interaction Modules.
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Property injection and constructor injection are both valid ways to get service dependencies.
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Because [AutocompleteHandler]s are constructed at service startup,
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class dependencies are resolved only once.
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> [!NOTE]
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> If you need to access per-request dependencies you can use the
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> IServiceProvider parameter of the `GenerateSuggestionsAsync()` method.
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[AutoCompleteHandler]: xref:Discord.Interactions.AutocompleteHandler
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[AutoCompleteAttribute]: xref:Discord.Interactions.AutocompleteAttribute
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