Type Adapters¶

TypeAdapters are a part of the execution chain. They are used to adapt the input of a slash command to the correct type needed to invoke the method.

Default Type Adapters¶

JDA-Commands uses Proteus for its type adapting system. Proteus supports all widening and narrowing primitive conversions as defined by the Java Language Specification. Additionally, JDA-Commands has implemented default type adapters for JDAs GuildChannel and its subtypes.

Thus, you can add all primitive types and their respective wrapper types as well as any underlying type of the OptionType enum as a parameter to your slash command methods. See Command Options for details.

Writing Own Type Adapters¶

As mentioned above, JDA-Commands uses Proteus under the hood for type adapting. The TypeAdapter interface is simply a subtype of Proteus' UniMapper. The following example only covers the registration part for JDA-Commands. Please refer to the documentation of Proteus for implementation details.

Example

CommandType Adapter (@Implementation Registration)Type Adapter (Builder Registration)

@Command("example")
public void onCommand(CommandEvent event, UserProfile profile) {
    ...
}

@Implementation.TypeAdapter(source = String.class, target = UserProfile.class)
public class UserProfileTypeAdapter implements TypeAdapter<String, UserProfile> {

    public MappingResult<UserProfile> from(String source, MappingContext<String, UserProfile> context) {
        return MappingResult.lossless(new UserProfile(source));
    }

}

public class UserProfileTypeAdapter implements TypeAdapter<String, UserProfile> {

    public MappingResult<CustomType> from(String source, MappingContext<String, UserProfile> context) {
        return MappingResult.lossless(new UserProfile(source));
    }

}

JDACommands.builder(jda, Main.class)
    .adapter(String.class, UserProfile.class, new UserProfileTypeAdapter());
    .start();

Tip

If your type adapter is simple enough, you could also just use lambda expressions:

JDACommands.builder(jda, Main.class)
    .adapter(String.class, UserProfile.class, (source, _) -> MappingResult.lossless(new UserProfile(source)));
    .start();

Your own types will be mapped to OptionType.STRING by default. You can override this mapping by using the @Param annotation.

Example

@Command("example")
public void onCommand(CommandEvent event, @Param(type = OptionType.USER) UserProfile profile) {
    ...
}

For our example this would also mean that we would need to update the UserProfileTypeAdapter to use User instead of String as its source type.

Error Messages¶

If the type adapting fails an error message will be sent to the user:

Type Adapter Error Message

You can customize this error message, find more about it here.