TypeError: Cannot read property 'id' of undefined of discord.js

Question

So I'm trying to have all my events in separate files. Events like "ready" and "messageCreate" are working just fine, but I can't figure this one out. Can someone please help me?

   const { MessageEmbed } = require("discord.js")
    
    module.exports = {
        name: "guildMemberAdd",
        run: async (member) => {
            const welcome = new MessageEmbed()
            .setDescription(`
        <:nezuko_peek:974066160108732517> — New friend just showed up: <@${member.user.id}>
        
        Welcome fellow adventurer in **Cozy corner**! What brings you in these sides? <:girl_love:973968823449436190> Here, go to <#972618593294512128> to introduce yourself and talk with us in <#971800237507248158>!
        `)
            .setImage("https://64.media.tumblr.com/01a9f72f062feaafa60cdbf80f9ba729/tumblr_inline_orgoyznIM51sd5e91_500.gif")
            .setColor("#F7DF79")
            .setFooter({ text: "Thank you for joining and enjoy your stay!" })
        
            const channel = member.guild.channels.cache.get("971800237507248158")
        
        channel.send({ content: `<@&974343947105206382>`, embeds: [welcome] })
        }
    }

This event called "guildMemberAdd" should be working and execute itself when member joins the server. Here's my event handler:

const { getFiles } = require("../util/functions")

module.exports = (bot, reload) => {
    const {client} = bot

    let events = getFiles("./events/", ".js")

    if (events.length === 0){
        console.log("No events to load")
    }

    events.forEach((f, i) => {
        if (reload)
        delete require.cache[require.resolve(`../events/${f}`)]
        const event = require(`../events/${f}`)
        client.events.set(event.name, event)

        if (!reload)
        console.log (`${i + 1}. ${f} loaded`)

    })

    if (!reload)
    initEvents(bot)
}

function triggerEventHandler(bot, event, ...args){
    const {client} = bot
    
    try {
        if (client.events.has(event))
        client.events.get(event).run(bot, ...args)
        else
        throw new Error(`Event ${event} does not exist`)
    }
    catch(err){
        console.error(err)
    }
}

function initEvents(bot) {
    const {client} = bot
    
    client.on("ready", () => {
        triggerEventHandler(bot, "ready")
    })

    client.on("messageCreate", (message) => {
        triggerEventHandler(bot, "messageCreate", message)
    })

    client.on("guildMemberAdd", (member) => {
        triggerEventHandler(bot, "guildMemberAdd", member)
    })
}

But for some reason it's not working and I got error: TypeError: Cannot read property 'id' of undefined

Answer 1

When you are calling your command, you are passing two arguments bot and ...args while in your exported command, it is only expecting ...args. So you have two options: either change the order of the arguments you are passing so that it is something like this: client.events.get(event).run(...args, bot), or remove the bot argument as you are not using it in the command anyway. Your final code in your event handler might look something like this:

const { getFiles } = require("../util/functions");

module.exports = (bot, reload) => {
  const { client } = bot;

  let events = getFiles("./events/", ".js");

  if (events.length === 0) {
    console.log("No events to load");
  }

  events.forEach((f, i) => {
    if (reload) delete require.cache[require.resolve(`../events/${f}`)];
    const event = require(`../events/${f}`);
    client.events.set(event.name, event);

    if (!reload) console.log(`${i + 1}. ${f} loaded`);
  });

  if (!reload) initEvents(bot);
};

function triggerEventHandler(bot, event, ...args) {
  const { client } = bot;

  try {
    if (client.events.has(event)) client.events.get(event).run(...args);
    else throw new Error(`Event ${event} does not exist`);
  } catch (err) {
    console.error(err);
  }
}

function initEvents(bot) {
  const { client } = bot;

  client.on("ready", () => {
    triggerEventHandler(bot, "ready");
  });

  client.on("messageCreate", (message) => {
    triggerEventHandler(bot, "messageCreate", message);
  });

  client.on("guildMemberAdd", (member) => {
    triggerEventHandler(bot, "guildMemberAdd", member);
  });
}

Answer 2

You should use listBox.SelectedItem.ToString() instead of SelectedValue.

So, you want to select an item from a ListBox and display it in a TextBox?

---

This is the beginner solution to the problem.

Additionally, you have to subscribe to the SelectionChanged event of the ListBox.

XAML:

<TextBox x:Name="textbox" />
<ListBox x:Name="listBox" SelectionChanged="ListBox_SelectionChanged"/>

Code Behind:

public partial class MainWindow : Window
{
    private readonly List<string> _cities;
    public MainWindow()
    {
        InitializeComponent();
        cities = new List<string>
        {
            "myCity1",
            "myCity2",
            "myCity3",
            "myCity4"
        };
        listBox.ItemsSource = _cities;
        }

    // Gets called every time the selection of the ListBox changes.
    private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        textbox.Text = listBox.SelectedItem.ToString();
    }
}

---

The same effect can be achieved using data-binding.

XAML:

<TextBox x:Name="textbox" Text="{Binding SelectedCity}" />
<ListBox x:Name="listBox" SelectedItem="{Binding SelectedCity}" />

Code-behind:

public partial class MainWindow : Window, INotifyPropertyChanged
{
    private readonly List<string> _cities;
    private string? _selectedCity;

    public event PropertyChangedEventHandler? PropertyChanged;

    public string SelectedCity
    {
        get => _selectedCity ??= string.Empty;
        set
        {
            _selectedCity = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedCity)));
        }
    }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        _cities = new List<string>
        {
            "myCity1",
            "myCity2",
            "myCity3",
            "myCity4"
        };
        listBox.ItemsSource = _cities;
    }
}

Use whichever works best for your use case.