Calling Rust from Lua
To call a rust function from Lua first you need to register a function within Rust using builder pattern.
use bevy::prelude::*; use bevy_scriptum::prelude::*; use bevy_scriptum::runtimes::lua::prelude::*; fn main() { App::new() .add_plugins(DefaultPlugins) .add_scripting::<LuaRuntime>(|runtime| { // `runtime` is a builder that you can use to register functions }) .run(); }
For example to register a function called my_rust_func
you can do the following:
use bevy::prelude::*; use bevy_scriptum::prelude::*; use bevy_scriptum::runtimes::lua::prelude::*; fn main() { App::new() .add_plugins(DefaultPlugins) .add_scripting::<LuaRuntime>(|runtime| { runtime.add_function(String::from("my_rust_func"), || { println!("my_rust_func has been called"); }); }) .run(); }
After you do that the function will be available to Lua code in your spawned scripts.
my_rust_func()
Registered functions can also take parameters. A parameter can be any type
that implements FromLua
.
Since a registered callback function is a Bevy system, the parameters are passed
to it as In
struct with tuple, which has to be the first parameter of the closure.
use bevy::prelude::*; use bevy_scriptum::prelude::*; use bevy_scriptum::runtimes::lua::prelude::*; fn main() { App::new() .add_plugins(DefaultPlugins) .add_scripting::<LuaRuntime>(|runtime| { runtime.add_function(String::from("func_with_params"), |args: In<(String, i64)>| { println!("my_rust_func has been called with string {} and i64 {}", args.0.0, args.0.1); }); }) .run(); }
To make it look nicer you can destructure the In
struct.
use bevy::prelude::*; use bevy_scriptum::prelude::*; use bevy_scriptum::runtimes::lua::prelude::*; fn main() { App::new() .add_plugins(DefaultPlugins) .add_scripting::<LuaRuntime>(|runtime| { runtime.add_function(String::from("func_with_params"), |In((a, b)): In<(String, i64)>| { println!("my_rust_func has been called with string {} and i64 {}", a, b); }); }) .run(); }
The above function can be called from Lua
func_with_params("abc", 123)
Return value via promise
Any registered rust function that returns a value will retrurn a promise when
called within a script. By calling :and_then
on the promise you can register
a callback that will receive the value returned from Rust function.
use bevy::prelude::*; use bevy_scriptum::prelude::*; use bevy_scriptum::runtimes::lua::prelude::*; fn main() { App::new() .add_plugins(DefaultPlugins) .add_scripting::<LuaRuntime>(|runtime| { runtime.add_function(String::from("returns_value"), || { 123 }); }) .run(); }
returns_value():and_then(function (value)
print(value) -- 123
end)