Lua Academy · Lesson

Data-Driven Config and Hot-Reload

Load game data from Lua files and reload scripts at runtime.

Data-Driven Config and Hot-Reload is a free Lua Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Lua Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What Is Data-Driven Design?

Data-driven design separates what (data: stats, levels, layouts) from how (code: game logic). Data changes do not require recompilation.

Loading Config from a Lua File

A config file is a Lua script that returns a table. Load it with dofile or loadfile + pcall.

-- config.lua
return {
  playerSpeed = 200,
  gravity     = 980,
  maxEnemies  = 10,
}

Reading the Config

In the host script, load and use the config table.

local config = dofile("config.lua")
print(config.playerSpeed)  -- 200

Sandboxed Config Loading

For security, load config in a restricted environment so malicious code cannot call os.execute or other dangerous functions.

local function loadConfig(filename)
  local chunk, err = loadfile(filename)
  if not chunk then error(err) end
  local env = {math = math, table = table}
  setfenv and setfenv(chunk, env) or _ENV  -- 5.1 vs 5.2+
  return chunk()
end

Hot-Reload Overview

Hot-reload allows changing data (or code) while the game is running. This dramatically speeds up iteration: tweak a value, see the result immediately without restarting.

Detecting File Changes

Use os.difftime(os.time(), lastModified) or poll a file's modification time with a C extension or I/O trick to detect when a config file has changed.

Reloading the Config

On change, reload the file and update the live config table in-place so all references to the table see the new values.

local function hotReload(config, filename)
  local ok, newCfg = pcall(dofile, filename)
  if ok and type(newCfg) == "table" then
    for k, v in pairs(newCfg) do config[k] = v end
    print("Config reloaded")
  else
    print("Reload error:", newCfg)
  end
end

Reloading Lua Modules

Remove a module from package.loaded before calling require again to force a fresh load.

package.loaded["mymodule"] = nil
local mymodule = require("mymodule")

Level Data from Lua

Define levels as Lua tables: room layouts, enemy placements, trigger zones. Load at runtime with dofile for fast iteration.

-- level1.lua
return {
  name = "Forest",
  enemies = {
    {type="goblin", x=100, y=200},
    {type="troll",  x=300, y=150},
  },
  music = "forest_theme.ogg",
}

Validation

After loading config, validate required fields and types. Provide clear error messages for missing or malformed data.

Version Tags

Include a version field in config files. Reject files with incompatible versions to prevent silent errors from stale data.

Hot-Reload Question

How do you force Lua to reload a cached module?

Recap: Data-Driven Config and Hot-Reload

Load game data from Lua files with dofile/loadfile. Use sandboxed environments for untrusted configs. Implement hot-reload by polling file modification times and clearing package.loaded for module reloads.

Frequently asked questions

Is the “Data-Driven Config and Hot-Reload” lesson free?

Yes — the full text of “Data-Driven Config and Hot-Reload” is free to read here on the web, and the Lua Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Lua Academy course, upgrade to CoddyKit PRO.

What will I learn in “Data-Driven Config and Hot-Reload”?

Load game data from Lua files and reload scripts at runtime. You practise Lua Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Lua Academy?

No prior experience is required. Lua Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Data-Driven Config and Hot-Reload” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Lua Academy lesson?

Yes. Every Lua Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

← Back to Lua Academy