bevy_scriptum/book/src/ruby/hello_world.md

Hello World

After you are done installing the required crates, you can start developing your first game or application using bevy_scriptum.

To start using the library you need to first import some structs and traits with Rust use statements.

For convenience there is a main "prelude" module provided called bevy_scriptum::prelude and a prelude for each runtime you have enabled as a create feature.

You can now start exposing functions to the scripting language. For example, you can expose a function that prints a message to the console:

# extern crate bevy;
# extern crate bevy_scriptum;

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_print"),
               |In((x,)): In<(String,)>| {
                   println!("my_print: '{}'", x);
               },
           );
        })
        .run();
}

Then you can create a script file in assets directory called script.lua that calls this function:

my_print("Hello world!")

And spawn an entity with attached Script component with a handle to a script source file:

# extern crate bevy;
# extern crate bevy_scriptum;

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_print"),
               |In((x,)): In<(String,)>| {
                   println!("my_print: '{}'", x);
               },
           );
        })
        .add_systems(Startup,|mut commands: Commands, asset_server: Res<AssetServer>| {
            commands.spawn(Script::<LuaScript>::new(asset_server.load("script.lua")));
        })
        .run();
}

You should then see my_print: 'Hello world!' printed in your console.