C# calling Lua

Use LuaAppDomain.GetFunction<T> to obtain a bound Delegate by module and method name, then invoke it. The API is the same in Editor and Player.

Canonical: Bootstrap.cs

Basic usage

var main = LuaAppDomain.GetFunction<Action>("app", "main");
main();

var add = LuaAppDomain.GetFunction<Func<int, int, int>>("app", "add");
int sum = add(10, 20);

local function add(a, b)
    return a + b
end

return {
    main = main,
    add = add,
}

Rule	Notes
Call `Initialize` first	Otherwise an exception is thrown
`T : MulticastDelegate`	Concrete `Action` / `Func` / custom delegates
module / method	`"app","add"` ↔ `return { add = ... }`
Caching	Cache yourself on hot paths; same instance is not guaranteed
Timing	Must be after `Initialize`; do not put in a static field initializer on the same type as `RuntimeInitializeOnLoadMethod`

Module loading

GetFunction("app", …) requires LoadLuaModule("app") to return source.

Environment	Typical path
Editor	`{ProjectRoot}/LuaScripts/app.lua`
Player	`StreamingAssets/LuaScripts/app.lua.txt`

private static string LoadLuaModule(string module)
{
#if UNITY_EDITOR
    string path = Path.Combine(Application.dataPath, "..", "LuaScripts", module + ".lua");
#else
    string path = Path.Combine(
        Application.streamingAssetsPath, "LuaScripts", module + ".lua.txt");
#endif
    return File.Exists(path) ? File.ReadAllText(path, Encoding.UTF8) : null;
}

Key points:

Modules must return { key = fn }; the key name = GetFunction’s method
Nested paths: module.Replace('.', '/') (e.g. battle.ai)
Sync before Player builds; see Build workflow
For hot reload / clearing the script world use LuaAppDomain.Reset(loader) (takes effect at EndOfFrame; old GetFunction delegates are invalid and must be rebound); no longer supports “swap loader only” on an already-initialized domain. Note StreamingAssets is read-only on Android

Multiple modules

var appMain = LuaAppDomain.GetFunction<Action>("app", "main");
var battleTick = LuaAppDomain.GetFunction<Action<float>>("battle", "tick");

Compared with “function as a parameter”

Scenario	Approach
C# actively calls a Lua-exported function	`GetFunction<T>(module, method)`
C# parameter is `Action`/`Func`, Lua passes `function`	Implicit marshal; see Function
Lua already has a function; need a specific delegate type	`zlua.to_delegate`

Common mistakes

Symptom	Fix
`module 'app' not found`	Editor/Player paths; whether Sync ran
GetFunction result invalid / call has no effect	Not Initialize’d; return-table key mismatch
Old scripts still running	Player not re-Synced

Learning path


Previous	Lua calling C#
Next	Value types

Basic usage​

Module loading​

Multiple modules​

Compared with “function as a parameter”​

Common mistakes​

Learning path​

Related​