Argument Parsers

By default, arguments are provided as strings.

Argument values can be automatically parsed into other types using the @parser() decorator:

@command("squared")
export class Squared extends TextCommand {
  @arg()
  @parser(IntegerParser)
  input!: number;

  async execute() {
    const square = this.input * this.input;
    return this.reply(`${this.input} squared is ${square}.`);
  }
}

If the argument cannot be parsed, a message will be sent to the user reporting the problem.

Built-in Parsers

There are a number of built-in parsers available:

• ChannelParser: a Discord channel
• ChannelIdParser: a Discord channel ID
• FloatParser: a floating-point number
• GuildChannelParser: a Discord channel of the current Guild
• IntegerParser: a integer number
• MemberParser: a User of the current Guild
• RoleParser: a Role of the current Guild
• RoleIdParser: the ID of a Role of the current Guild
• String: any string, the default parser
• User: a Discord user
• UserId a Discord user ID

Default Parsers

By default, a number of field types have automatically associated parsers.

In the above example, Hades will observe the field's type is number and automatically use the IntegerParser. So the @parser(IntegerParser) bit can be removed:

@command("squared")
export class Squared extends TextCommand {
  @arg()
  input!: number; // automatically parsed with IntegerParser

  async execute() {
    const square = this.input * this.input;
    return this.reply(`${this.input} squared is ${square}.`);
  }
}

Here are the default type-parser associations:

• string => StringParser
• number => IntegerParser
• Channel => ChannelParser
• User => UserParser
• Role => RoleParser
• GuildChannel => GuildChannelParser
• GuildMember => MemberParser

You can provide your own mapping by providing it to TextCommandsInstaller:

const container = new HadesContainer({
  installers: [
    new TextCommandsInstaller([...defaultMappedTypes, [Number, FloatParser]]),
  ],
});

Now the Squared command above would only accept floating-point numbers.

Custom Parsers

You can also implement your own parsers by extending the Parser class:

@parser()
export class YoutubeVideo extends TextArgParser {
  name = "youtube video";
  description = "A YouTube Video";

  async parse(arg: TextArgInstaller, context: TextCommandContext) {
    const value = context.reader.getString();
    const match = value.match(/^([\w-]{11})(?:\S+)?$/);
    if (!match) {
      throw new TextArgError("Invalid YouTube video ID.");
    }
    return new YoutubeVideo(match[1]);
  }
}

If the argument cannot be parsed, a TextArgError can be thrown.

Manually Parsing Arguments

Instead of using decorated fields, you can also manually parse arguments passed to your commands using the CommandContext.reader attribute.

CommandContext.reader is a parser from discord-command-parser.

This can parse arguments in a more structured way, including user and channel IDs.

• getString()
• getInt()
• getFloat()
• getRemaining()
• getUserID()
• getRoleID()
• getChannelID()
• seek( amount: number = 1 ): Useful for skipping tokens