Creating TypeSafe event emitter wrapper function

I have this file EventTypes.ts:

import type { GuildBan, GuildMember } from 'discord.js';
import type { BanExportOptions, BanImportOptions } from './typeDefs';

export const BUEvents = {
  BanListExport: 'banListExport' as const,
  BanListImport: 'banListImport' as const,
  BotGuildBanAdd: 'botGuildBanAdd' as const,
} as const;

export interface BUEventParams {
  [BUEvents.BanListExport]: [payload: BanExportOptions];
  [BUEvents.BanListImport]: [payload: BanImportOptions];
  [BUEvents.BotGuildBanAdd]: [ban: GuildBan, executor: GuildMember];
}

declare module 'discord.js' {
  interface ClientEvents extends BUEventParams {}
}

import type { GuildBan, GuildMember } from 'discord.js';
import type { BanExportOptions, BanImportOptions } from './typeDefs';

export const BUEvents = {
  BanListExport: 'banListExport' as const,
  BanListImport: 'banListImport' as const,
  BotGuildBanAdd: 'botGuildBanAdd' as const,
} as const;

export interface BUEventParams {
  [BUEvents.BanListExport]: [payload: BanExportOptions];
  [BUEvents.BanListImport]: [payload: BanImportOptions];
  [BUEvents.BotGuildBanAdd]: [ban: GuildBan, executor: GuildMember];
}

declare module 'discord.js' {
  interface ClientEvents extends BUEventParams {}
}

And I'm trying to create a wrapper function emitBotEvent()

export function emitBotEvent<E extends keyof ClientEvents>(
  event: keyof typeof BUEvents,
  ...args: BUEventParams[E]
) {
  container.client.emit(event, args);
}

export function emitBotEvent<E extends keyof ClientEvents>(
  event: keyof typeof BUEvents,
  ...args: BUEventParams[E]
) {
  container.client.emit(event, args);
}

What I'm trying to do is, if I put BUEvents.BanListImport, the 2nd parameter of emitBotEvent() function should expect the type [payload: BanImportOptions] And if I put BUEvents.BotGuildBanAdd, the type shuold become [ban: GuildBan, executor: GuildMember] I tried the above way, it doesn't work thonk

1 Reply

MRDGH2821OP•2y ago

I think I got resonable amount of type safety with this:

export function emitBotEvent<E extends keyof BUEventParams>(
  event: keyof typeof BUEvents,
  ...args: BUEventParams[E]
) {
  container.client.emit(event, ...args);
}

export function emitBotEvent<E extends keyof BUEventParams>(
  event: keyof typeof BUEvents,
  ...args: BUEventParams[E]
) {
  container.client.emit(event, ...args);
}

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Creating TypeSafe event emitter wrapper function