Preconditions

Precondition logic is the same as it is for Text-based commands. A list of attributes and usage is still given for people who are new to both.

There are two types of Preconditions you can use:

• PreconditionAttribute can be applied to Modules, Groups, or Commands.
• ParameterPreconditionAttribute can be applied to Parameters.

You may visit their respective API documentation to find out more.

Bundled Preconditions

Discord.Interactions ships with several bundled Preconditions for you to use.

• RequireContextAttribute
• RequireOwnerAttribute
• RequireBotPermissionAttribute
• RequireUserPermissionAttribute
• RequireNsfwAttribute
• RequireRoleAttribute
• RequireTeamAttribute
• DoHierarchyCheckAttribute

Using Preconditions

To use a precondition, simply apply any valid precondition candidate to a command method signature as an attribute.

[RequireOwner]
[SlashCommand("hi")]
public Task SayHiAsync() => RespondAsync("hello owner!");

ORing Preconditions

When writing commands, you may want to allow some of them to be executed when only some of the precondition checks are passed.

This is where the Group property of a precondition attribute comes in handy. By assigning two or more preconditions to a group, the command system will allow the command to be executed when one of the precondition passes.

Example - ORing Preconditions

// The following example only requires the user to either have the
// Administrator permission in this guild or own the bot application.
[RequireUserPermission(GuildPermission.Administrator, Group = "Permission")]
[RequireOwner(Group = "Permission")]
public class AdminModule : ModuleBase<SocketCommandContext>
{
    [Command("ban")]
    public Task BanAsync(IUser user) => Context.Guild.AddBanAsync(user);
}

Custom Preconditions

To write your own Precondition, create a new class that inherits from either PreconditionAttribute or ParameterPreconditionAttribute depending on your use.

In order for your Precondition to function, you will need to override the CheckPermissionsAsync method.

If the context meets the required parameters, return PreconditionResult.FromSuccess, otherwise return PreconditionResult.FromError and include an error message if necessary.

Note

Visual Studio can help you implement missing members from the abstract class by using the "Implement Abstract Class" IntelliSense hint.