Prechecks
Learn how to use prechecks to add additional validation and checks before a command runs.
Prechecks are a powerful feature in Carbon that allow you to add additional validation and checks before a command is executed. This can be useful for implementing features like cooldowns, permission checks, or any other validation that needs to happen before the main command logic runs.
How Prechecks Work
Prechecks are implemented by overriding the preCheck method in your command class. This method is called before the main run method of your command. If the precheck returns anything other than true, the command will not execute.
Here's a basic example of a precheck:
import { Command } from "@buape/carbon"
import { CommandInteraction } from "discord.js"
export default class MyCommand extends Command {
public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
// Check if the user has a specific role
if (!interaction.member?.roles.find(x => x.id === "123456789")) {
await interaction.reply("You don't have permission to use this command!")
return false
}
return true
}
public override async run(interaction: CommandInteraction) {
// Your command logic here
}
}Common Use Cases
Cooldowns
You can implement cooldowns using prechecks to prevent users from spamming commands:
private cooldowns = new Map<string, number>()
public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
const cooldown = 5000 // 5 seconds
const now = Date.now()
const lastUsed = this.cooldowns.get(interaction.user.id)
if (lastUsed && now - lastUsed < cooldown) {
await interaction.reply(`Please wait ${Math.ceil((cooldown - (now - lastUsed)) / 1000)} seconds before using this command again.`)
return false
}
this.cooldowns.set(interaction.user.id, now)
return true
}Permission Checks
You can use prechecks to verify if a user has the necessary permissions to use a command:
public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
if (!interaction.memberPermissions?.has("Administrator")) {
await interaction.reply("You need administrator permissions to use this command!")
return false
}
return true
}Maintenance Mode
You can implement a maintenance mode that prevents commands from being used:
private maintenanceMode = false
public override async preCheck(interaction: CommandInteraction): Promise<true | unknown> {
if (this.maintenanceMode) {
await interaction.reply("This command is currently under maintenance. Please try again later.")
return false
}
return true
}Last updated on