Frameworks: ESX and QBCore · Lesson 3/5 · 9 min

ESX callbacks: requesting data from the server

When the client needs an answer from the server (do I have balance? what items do I have?), you use a callback.

A normal event is one-way (the client notifies the server). But sometimes the client needs a RESPONSE: «do I have enough money for this?». That's what server callbacks are for.

On the server: register the callback

lua

ESX.RegisterServerCallback('tienda:comprar', function(source, cb, precio)
  local xPlayer = ESX.GetPlayerFromId(source)
  if not xPlayer then return cb(false) end
  if xPlayer.getMoney() >= precio then
    xPlayer.removeMoney(precio)
    cb(true)   -- respond to the client: purchase OK
  else
    cb(false)  -- no money
  end
end)

server.lua

On the client: call it and wait for the response

lua

ESX.TriggerServerCallback('tienda:comprar', function(exito)
  if exito then
    print('Purchase completed')
  else
    print('Not enough money')
  end
end, 1500) -- 1500 = price passed to the server

client.lua

The decision (does the player have money?) and the charge happen on the SERVER. The client only receives yes/no. That way cheating is impossible.

Practice what you learned

0/3

Ordena el código

Ordena un callback de servidor que cobra un precio solo si el jugador tiene dinero.

Coloca las líneas en el orden correcto con las flechas.

local xPlayer = ESX.GetPlayerFromId(source)

end)

if xPlayer.getMoney() >= precio then xPlayer.removeMoney(precio) cb(true) else cb(false) end

ESX.RegisterServerCallback('tienda:comprar', function(source, cb, precio)

if not xPlayer then return cb(false) end

Pista

Primero registras el callback, luego obtienes el jugador, validas y respondes con cb().

Rellena los huecos

Completa la llamada del cliente que pide al servidor y espera la respuesta.

1ESX.('tienda:comprar', function(exito)

2 if exito then print('Compra OK') end

3end, 1500)

Pista

Es la pareja cliente de RegisterServerCallback; el 1500 es el precio que se pasa al servidor.

Test

En un callback de ESX, ¿dónde se decide si el jugador tiene dinero y se le cobra?

Challenge: code it yourself

Create a callback that returns true only if the player has the 'police' job.

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

Compare xPlayer.job.name == 'police' and respond with cb(true/false).

Escribe aquí tu solución:

← ESX on the server: the player and their money Next: Jobs with ESX

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