discord.js guildCreate.js 事件未触发

Question

We're trying to get our guildCreate.js event trigger working for Corion. But it's throwing the following error:

3|Corion   | (node:16154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'cache' of undefined

Here is our code:

module.exports = async (client, guild) => {
    const channel = guild.channels.cache.find(channel => channel.type === 'text' && channel.permissionsFor(guild.me).has('SEND_MESSAGES'))
    console.log(`${client.name}` + `has entered` + `${guild.name}.`)
    channel.send(`Thanks for invite me!\n\nType **c!help** to see a full list of available commands!`).catch(console.error)
};

This is our events handler if it helps:

const events = fs.readdirSync('./events').filter(file => file.endsWith('.js'));

for (const file of events) {
    console.log(`Loading discord.js event ${file}`);
    const event = require(`./events/${file}`);
    client.on(file.split(".")[0], event.bind(null, client));
};

We're running discord.js: 12.5.1

Answer 1

This won't work in this particular situation because of how the callback of client.on("guildCreate") works. In fact, you may find that this will not work properly for pretty much all of the different events of Discord because of how the callbacks work in combination with how you are using .bind() .

The Problem

Think about how client.on() works in terms of its callback. When using client.on() you do something like this: client.on("guildCreate", callback) . And this is what client.on() does when that event is triggered: it calls callback(guild) .

Now think about what you're doing in your code. You're doing event.bind(null, client) on your event handler function, which is in the form callback(client, guild) . So this is what happens:

1. You set the value of client in your callback to your Discord.Client , via .bind() . So now your client parameter is Discord.Client , and your guild parameter is undefined .
2. When the event is triggered, it now sets your first parameter ( client ) to a Guild object. So now your client parameter is Guild and your guild parameter is still undefined .
3. Now in your callback, you try to do guild.channels.cache . guild is still undefined, so guild.channels is undefined, and therefore you get the error: Cannot read property 'cache' of undefined .

The Solution

Alright, so how do you solve this issue? Well, your first instinct might be to simply switch the order of your client and guild parameters in your callback, and then tweak your .bind() appropriately. That might work for this particular event, but remember that some events have two or more parameters in their callbacks. guildCreate only sends you a single guild argument, but something like guildUpdate would send you two (consequently causing the exact same error you are currently experiencing).

No matter what solution to this you pursue, you will need to scrap the client parameter altogether. If you want to account for any number of parameters and still use the convenient .bind() method, then instead of binding your client to the first parameter of the callback, you could instead bind your client to the this keyword. Here's an example of what I mean by that:

Event handler:

const events = fs.readdirSync('./events').filter(file => file.endsWith('.js'));

for (const file of events) {
    console.log(`Loading discord.js event ${file}`);
    const event = require(`./events/${file}`);
    client.on(file.split(".")[0], event.bind(client));
};

guildCreate.js:

module.exports = async function (guild) {
    const client = this;
    const channel = guild.channels.cache.find(channel => channel.type === 'text' && channel.permissionsFor(guild.me).has('SEND_MESSAGES'))
    console.log(`${client.user.username}` + `has entered` + `${guild.name}.`)
    channel.send(`Thanks for invite me!\n\nType **c!help** to see a full list of available commands!`).catch(console.error)
};

This should ensure that client.on() doesn't mess with the value of client , and therefore fix the specific error you are experiencing.

What Changed

So overall, you need to: change .bind(null, client) to .bind(client) in your event handler, remove the client parameter from your guildCreate.js callback, use this to access your client, change client.name to client.user.username because the former is incorrect, and switch from ES6 arrow functions ( () => {} ) to the standard function syntax ( function() {} ) because of how the this keyword works within the former.

I have not tested this solution, but it should hypothetically work to at least solve the error you are currently facing. Let me know if it doesn't, or if there are other relevant errors in this code, and I will edit the answer to fix them.