⏺️ Getting Started with Lua

Introduction to Lua programming for RedM and RSG Framework

What is Lua?

Lua is a lightweight, high-level scripting language designed for embedded use in applications. RedM (and FiveM) use Lua 5.4 as their primary scripting language for creating game modifications and server resources.

Lua is easy to learn, fast to execute, and powerful enough to create complex game systems. It’s the perfect language for RedM development!

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Client vs Server Scripts

RedM resources can have client scripts, server scripts, or both. Understanding the difference is crucial:

Client Scripts

• Run on each player’s machine independently
• Handle visual effects, UI, local player actions
• Cannot directly access server data or other players
• File location: client/ folder or defined as client_script in fxmanifest.lua

Server Scripts

• Run once on the server
• Handle game logic, database operations, player data
• Manage communication between players
• File location: server/ folder or defined as server_script in fxmanifest.lua

Shared Scripts

• Run on both client and server
• Used for shared configurations, item definitions, etc.
• File location: shared/ folder or defined as shared_script in fxmanifest.lua

Clients cannot communicate directly with each other. All communication must go through the server using events.

Example Flow:

Client A → Server Event → Server Processing → Client Event → Client B

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Basic Lua Syntax

Variables

-- Local variables (recommended - faster and scoped)
local playerName = 'John Doe'
local playerAge = 25
local isAlive = true

-- Global variables (avoid unless necessary)
globalVariable = 'I am global'

Always use local variables unless you specifically need a global variable. Global variables can cause conflicts and performance issues.

Data Types

-- Strings
local message = 'Hello, RedM!'
local message2 = "Double quotes work too"
local longText = [[
    Multi-line strings
    use double brackets
]]

-- Numbers
local health = 100
local armor = 50.5
local money = 1000

-- Booleans
local isDead = false
local isAdmin = true

-- Tables (arrays and dictionaries)
local weapons = {'revolver', 'rifle', 'shotgun'}
local player = {
    name = 'John',
    age = 25,
    job = 'sheriff'
}

-- Nil (represents absence of value)
local nothing = nil

Comments

-- This is a single-line comment

--[[
    This is a
    multi-line comment
]]

--- This is a documentation comment (used for annotations)
---@param source number - Player server ID
---@return string - Player name

---

Functions

Defining Functions

-- Basic function
local function greet(name)
    print('Hello, ' .. name .. '!')
end

greet('Arthur') -- Output: Hello, Arthur!

-- Function with return value
local function add(a, b)
    return a + b
end

local sum = add(5, 3) -- sum = 8

-- Function with multiple return values
local function getCoords()
    return 100.0, 200.0, 30.0
end

local x, y, z = getCoords()

Anonymous Functions

-- Function assigned to variable
local multiply = function(a, b)
    return a * b
end

-- Callback function
TriggerEvent('someEvent', function(data)
    print('Received:', data)
end)

---

Control Structures

If Statements

local health = 50

if health <= 0 then
    print('Player is dead')
elseif health < 30 then
    print('Player is critically wounded')
elseif health < 70 then
    print('Player is injured')
else
    print('Player is healthy')
end

-- Logical operators
if health > 0 and armor > 0 then
    print('Player has health and armor')
end

if isDead or isUnconscious then
    print('Player cannot move')
end

if not isAdmin then
    print('Player is not an admin')
end

Loops

-- For loop (numeric)
for i = 1, 10 do
    print('Iteration:', i)
end

-- For loop with step
for i = 10, 1, -1 do
    print('Countdown:', i)
end

-- For loop (iterate over table array)
local weapons = {'revolver', 'rifle', 'shotgun'}
for index, weapon in ipairs(weapons) do
    print(index, weapon)
end

-- For loop (iterate over table dictionary)
local player = {
    name = 'John',
    age = 25,
    job = 'sheriff'
}
for key, value in pairs(player) do
    print(key, '=', value)
end

-- While loop
local count = 0
while count < 5 do
    print('Count:', count)
    count = count + 1
end

-- Repeat-until loop
local health = 100
repeat
    health = health - 10
    print('Health:', health)
until health <= 0

---

Tables (Arrays & Dictionaries)

Tables are Lua’s primary data structure - they can act as arrays, dictionaries, or both!

Arrays (Numeric Indices)

-- Creating an array
local weapons = {'revolver', 'rifle', 'shotgun'}

-- Accessing elements (Lua arrays start at 1, not 0!)
print(weapons[1]) -- Output: revolver
print(weapons[2]) -- Output: rifle

-- Adding elements
weapons[4] = 'bow'
table.insert(weapons, 'lasso') -- Adds to end

-- Removing elements
table.remove(weapons, 2) -- Removes 'rifle'

-- Get array length
local count = #weapons
print('Weapon count:', count)

Dictionaries (Key-Value Pairs)

-- Creating a dictionary
local player = {
    name = 'John Doe',
    age = 25,
    job = 'sheriff',
    money = 1000
}

-- Accessing values
print(player.name) -- Output: John Doe
print(player['age']) -- Output: 25

-- Adding/modifying values
player.job = 'deputy'
player['money'] = 1500

-- Nested tables
local character = {
    info = {
        firstname = 'John',
        lastname = 'Doe'
    },
    money = {
        cash = 500,
        bank = 2000
    }
}

print(character.info.firstname) -- Output: John
print(character.money.bank) -- Output: 2000

---

String Manipulation

-- Concatenation
local firstName = 'John'
local lastName = 'Doe'
local fullName = firstName .. ' ' .. lastName

-- String formatting (modern way)
local message = string.format('Hello %s, you have $%d', playerName, money)

-- String methods
local text = 'Hello World'
print(string.upper(text)) -- HELLO WORLD
print(string.lower(text)) -- hello world
print(string.len(text)) -- 11
print(string.sub(text, 1, 5)) -- Hello
print(string.find(text, 'World')) -- 7 11

-- String splitting (common pattern)
local function split(str, delimiter)
    local result = {}
    for match in (str .. delimiter):gmatch("(.-)" .. delimiter) do
        table.insert(result, match)
    end
    return result
end

local parts = split('apple,banana,orange', ',')
-- parts = {'apple', 'banana', 'orange'}

---

Math Operations

-- Basic arithmetic
local a = 10
local b = 3

print(a + b)  -- 13 (addition)
print(a - b)  -- 7 (subtraction)
print(a * b)  -- 30 (multiplication)
print(a / b)  -- 3.333... (division)
print(a % b)  -- 1 (modulus - remainder)
print(a ^ b)  -- 1000 (exponentiation)

-- Math library
print(math.abs(-10))     -- 10
print(math.ceil(3.2))    -- 4
print(math.floor(3.8))   -- 3
print(math.max(5, 10))   -- 10
print(math.min(5, 10))   -- 5
print(math.random(1, 10)) -- Random number between 1-10
print(math.sqrt(16))     -- 4

-- Rounding (common pattern)
local function round(num, decimals)
    local mult = 10 ^ (decimals or 0)
    return math.floor(num * mult + 0.5) / mult
end

print(round(3.14159, 2)) -- 3.14

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Creating Your First Resource

Step 1: Create Resource Folder

Create a folder in your resources directory:

resources/
  [myresources]/
    my-first-script/

Step 2: Create fxmanifest.lua

Every resource needs a manifest file:

fxmanifest.lua

fx_version 'cerulean'
game 'rdr3'
rdr3_warning 'I acknowledge that this is a prerelease build of RedM, and I am aware my resources *will* become incompatible once RedM ships.'

description 'My First Script'
version '1.0.0'

client_scripts {
    'client/client.lua'
}

server_scripts {
    'server/server.lua'
}

shared_scripts {
    'shared/config.lua'
}

Step 3: Create Your Scripts

shared/config.lua:

Config = {}

Config.WelcomeMessage = 'Welcome to my server!'
Config.MaxPlayers = 32

client/client.lua:

local RSGCore = exports['rsg-core']:GetCoreObject()

-- Code runs when resource starts
CreateThread(function()
    print('Client script loaded!')
end)

-- Listen for player spawn
AddEventHandler('RSGCore:Client:OnPlayerLoaded', function()
    print('Player loaded!')
    lib.notify({
        description = Config.WelcomeMessage,
        type = 'info'
    })
end)

server/server.lua:

local RSGCore = exports['rsg-core']:GetCoreObject()

-- Code runs when resource starts
print('Server script loaded!')

-- Register a command
RSGCore.Commands.Add('hello', 'Say hello', {}, false, function(source, args)
    local Player = RSGCore.Functions.GetPlayer(source)
    if not Player then return end

    TriggerClientEvent('chat:addMessage', source, {
        args = {'System', 'Hello ' .. Player.PlayerData.charinfo.firstname .. '!'}
    })
end)

-- Register an event
RegisterNetEvent('my-first-script:server:greet', function(message)
    local src = source
    print('Player ' .. src .. ' said: ' .. message)
end)

Step 4: Start Your Resource

Add to server.cfg:

ensure my-first-script

Or start it in-game:

restart my-first-script

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Common Mistakes to Avoid

1. Forgetting local keyword

-- Bad
playerName = 'John' -- Global variable!

-- Good
local playerName = 'John'

2. Array indexing starts at 1, not 0

local items = {'apple', 'banana', 'orange'}
print(items[0]) -- nil (wrong!)
print(items[1]) -- 'apple' (correct!)

3. Using == for string/table comparison

-- Numbers and booleans
if health == 100 then -- Correct

-- Strings are fine too
if name == 'John' then -- Correct

-- Tables need special handling
local t1 = {a = 1}
local t2 = {a = 1}
if t1 == t2 then -- Always false! Different references

4. Not checking for nil

-- Bad
local Player = RSGCore.Functions.GetPlayer(source)
print(Player.PlayerData.name) -- Error if Player is nil!

-- Good
local Player = RSGCore.Functions.GetPlayer(source)
if not Player then return end
print(Player.PlayerData.name) -- Safe

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Next Steps

Now that you understand Lua basics, explore these advanced topics:

• Events & Callbacks - Communication between client and server
• Threads & Loops - Creating continuous processes
• Table Operations - Advanced table manipulation
• Common Patterns - RSG Framework patterns and best practices
• Performance Tips - Optimize your code
• Debugging - Find and fix errors

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Practice makes perfect! Start with simple scripts and gradually add complexity as you learn.