Debug errors like a pro · Lesson 1/3 · 8 min

Read the error thoroughly

The FiveM error tells you the exact resource, file and line. Learn to read it at a glance.

Most people see a red error and panic. A pro reads it: it's almost always telling you exactly where to look.

text

SCRIPT ERROR: @mi_banco/server/main.lua:42: attempt to perform arithmetic on a nil value (local 'saldo')
> handler (@mi_banco/server/main.lua:42)

A real error

@mi_banco → the resource that's failing.
server/main.lua:42 → file and exact LINE. Go straight there.
attempt to perform arithmetic on a nil value → you tried to operate (+, -, *) with a nil.
(local 'saldo') → the guilty variable is 'saldo': it was nil when you did the math.

Translation: on line 42, 'saldo' was nil when doing a math operation. Typical cause: the DB query returned nothing and you didn't check it. You go to line 42, see where 'saldo' comes from and add a guard.

Client console: F8. Server console: the txAdmin window or txAdmin → Live Console. These errors show up there in real time.

Practice what you learned

0/3

Test

Lees: "attempt to perform arithmetic on a nil value (local 'saldo')". ¿Qué significa?

Pista

'nil value (local saldo)' te da hasta el nombre de la variable culpable.

Rellena los huecos

El saldo puede venir vacío de la BD. Completa el guard que evita el 'arithmetic on a nil value'.

1local saldo = MySQL.scalar.await('SELECT money FROM users WHERE id = ?', { id })

2if not then return end

3local nuevo = saldo + cantidad

Pista

Comprueba la MISMA variable que el error señala como nil antes de usarla.

Corrige el error

Peta con "attempt to index a nil value (local 'xPlayer')" porque el jugador no existía. Añade un guard antes de usar xPlayer.

Este código tiene un fallo:

1local xPlayer = ESX.GetPlayerFromId(src)

2local cash = xPlayer.getMoney()

Reescríbelo corregido:

Pista

ESX.GetPlayerFromId puede devolver nil; comprueba xPlayer antes de hacer xPlayer.algo.

Challenge: code it yourself

You're given: '@tienda/client.lua:18: attempt to call a nil value (field GetMoney)'. Say what it means and where to look.

Write it yourself in your editor (VS Code) and test it on your server. You learn here by doing it, not by copying.

See hint

A function/method called 'GetMoney' doesn't exist (typo? bad export?). Look at line 18 of client.lua.

Escribe aquí tu solución:

Next: print: your best friend for debugging

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