Callback

Usage

Promise-based client-server RPC system for seamless communication.

The Callback module provides a custom promise-based RPC (Remote Procedure Call) system for communication between client and server.

Overview

The callback system allows you to:

Call server functions from client and get return values
Call client functions from server and get return values
Use both synchronous (blocking) and asynchronous (non-blocking) patterns
Build clean, maintainable client-server communication

Server Functions

register

Registers a callback that can be called from the client.

FM.callback.register(eventName, callback)

eventName

string required

Unique name for the callback

callback

function required

Function(src, ...) to execute when called. Must return value(s).

Example:

-- Server-side registration
FM.callback.register('getPlayerMoney', function(src, moneyType)
    local player = FM.player.get(src)
    if not player then return 0 end

    return player.getMoney(moneyType or 'money')
end)

FM.callback.register('canAfford', function(src, amount)
    local player = FM.player.get(src)
    if not player then return false end

    return player.getMoney('bank') >= amount
end)

FM.callback.register('getOnlineCount', function(src, jobName)
    if jobName then
        return FM.framework.getPlayers({ job = jobName, count = true })
    else
        return FM.framework.getPlayers({ count = true })
    end
end)

async

Makes an asynchronous callback request to a client.

FM.callback.async(eventName, src, callback, ...)

eventName

string required

Name of the registered client callback

src

number required

Player source ID

callback

function required

Function to execute with the response

...

any

Arguments to pass to the client callback

Example:

-- Server-side async call
FM.callback.async('getVehicleInFront', src, function(vehicleData)
    if vehicleData then
        print("Vehicle model:", vehicleData.model)
        print("Vehicle plate:", vehicleData.plate)
    else
        print("No vehicle found")
    end
end)

sync

Makes a synchronous callback request to a client (blocks until response).

FM.callback.sync(eventName, src, ...)

eventName

string required

Name of the registered client callback

src

number required

Player source ID

...

any

Arguments to pass to the client callback

Returns: Response value(s) from the client

Example:

-- Server-side sync call
local coords = FM.callback.sync('getPlayerCoords', src)
if coords then
    print("Player is at:", coords.x, coords.y, coords.z)
end

local hasWeapon = FM.callback.sync('hasWeaponEquipped', src)
if hasWeapon then
    print("Player has weapon equipped")
end

Client Functions

register

Registers a callback that can be called from the server.

FM.callback.register(eventName, callback)

eventName

string required

Unique name for the callback

callback

function required

Function(...) to execute when called. Must return value(s).

Example:

-- Client-side registration
FM.callback.register('getPlayerCoords', function()
    return GetEntityCoords(PlayerPedId())
end)

FM.callback.register('hasWeaponEquipped', function()
    local ped = PlayerPedId()
    return GetSelectedPedWeapon(ped) ~= GetHashKey("WEAPON_UNARMED")
end)

FM.callback.register('getVehicleInFront', function()
    local ped = PlayerPedId()
    local coords = GetEntityCoords(ped)
    local forward = GetEntityForwardVector(ped)
    local rayHandle = StartShapeTestRay(
        coords.x, coords.y, coords.z,
        coords.x + forward.x * 5.0,
        coords.y + forward.y * 5.0,
        coords.z + forward.z * 5.0,
        10, ped, 0
    )

    local _, hit, _, _, vehicle = GetShapeTestResult(rayHandle)

    if hit and DoesEntityExist(vehicle) then
        return {
            model = GetEntityModel(vehicle),
            plate = GetVehicleNumberPlateText(vehicle),
            entity = vehicle
        }
    end

    return nil
end)

async

Makes an asynchronous callback request to the server.

FM.callback.async(eventName, callback, ...)

eventName

string required

Name of the registered server callback

callback

function required

Function to execute with the response

...

any

Arguments to pass to the server callback

Example:

-- Client-side async call
FM.callback.async('getPlayerMoney', function(money)
    print("You have $" .. money)
end, 'bank')

FM.callback.async('canAfford', function(canAfford)
    if canAfford then
        print("You can afford this!")
    else
        print("Not enough money")
    end
end, 5000)

sync

Makes a synchronous callback request to the server (blocks until response).

FM.callback.sync(eventName, ...)

eventName

string required

Name of the registered server callback

...

any

Arguments to pass to the server callback

Returns: Response value(s) from the server

Example:

-- Client-side sync call
local money = FM.callback.sync('getPlayerMoney', 'bank')
print("Bank balance: $" .. money)

local onlineCount = FM.callback.sync('getOnlineCount')
print("Players online:", onlineCount)

local policeCount = FM.callback.sync('getOnlineCount', 'police')
print("Police online:", policeCount)

Exports

Callback functions are available as exports:

-- Server
exports['fmLib']:callback_register(eventName, callback)
exports['fmLib']:callback_async(eventName, src, callback, ...)
exports['fmLib']:callback_sync(eventName, src, ...)

-- Client
exports['fmLib']:callback_register(eventName, callback)
exports['fmLib']:callback_async(eventName, callback, ...)
exports['fmLib']:callback_sync(eventName, ...)

Functions

Server-side society/shared account functions for managing organization funds.