Table of Contents

AutocompleteHandlers

AutocompleteHandlers provide a similar pattern to TypeConverters. AutocompleteHandlers are cached, singleton services and they are used by the Interaction Service to handle Autocomplete Interactions targeted to a specific Slash Command parameter.

To start using AutocompleteHandlers, use the [AutocompleteAttribute(Type type)] overload of the AutocompleteAttribute. This will dynamically link the parameter to the AutocompleteHandler type.

AutocompleteHandlers raise the AutocompleteHandlerExecuted event on execution. This event can be also used to create a post-execution logic, just like the *CommandExecuted events.

Creating AutocompleteHandlers

A valid AutocompleteHandlers must inherit AutocompleteHandler base type and implement all of its abstract methods.

// you need to add `Autocomplete` attribute before parameter to add autocompletion to it
[SlashCommand("command_name", "command_description")]
public async Task ExampleCommand([Summary("parameter_name"), Autocomplete(typeof(ExampleAutocompleteHandler))] string parameterWithAutocompletion)
    => await RespondAsync($"Your choice: {parameterWithAutocompletion}");

public class ExampleAutocompleteHandler : AutocompleteHandler
{
    public override async Task<AutocompletionResult> GenerateSuggestionsAsync(IInteractionContext context, IAutocompleteInteraction autocompleteInteraction, IParameterInfo parameter, IServiceProvider services)
    {
        // Create a collection with suggestions for autocomplete
        IEnumerable<AutocompleteResult> results = new[]
        {
            new AutocompleteResult("Name1", "value111"),
            new AutocompleteResult("Name2", "value2")
        };

        // max - 25 suggestions at a time (API limit)
        return AutocompletionResult.FromSuccess(results.Take(25));
    }
}

GenerateSuggestionsAsync()

The Interactions Service uses this method to generate a response of an Autocomplete Interaction. This method should return AutocompletionResult.FromSuccess(IEnumerable<AutocompleteResult>) to display parameter suggestions to the user. If there are no suggestions to be presented to the user, you have two results:

  1. Returning the parameterless AutocompletionResult.FromSuccess() will display a "No options match your search." message to the user.
  2. Returning AutocompleteResult.FromError() will make the Interaction Service not respond to the interaction, consequently displaying the user a "Loading options failed." message. AutocompletionResult.FromError() is solely used for error handling purposes. Discord currently doesn't allow you to display custom error messages. This result type will be directly returned to the AutocompleteHandlerExecuted method.

Resolving AutocompleteHandler Dependencies

AutocompleteHandler dependencies are resolved using the same dependency injection pattern as the Interaction Modules. Property injection and constructor injection are both valid ways to get service dependencies.

Because AutocompleteHandlers are constructed at service startup, class dependencies are resolved only once.

Note

If you need to access per-request dependencies you can use the IServiceProvider parameter of the GenerateSuggestionsAsync() method.

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