add example

Cargo.toml

@@ -185,6 +185,12 @@ name = "function_params_ruby"
 path = "examples/ruby/function_params.rs"
 required-features = ["ruby"]
 
+[[example]]
+name = "function_return_value_ruby"
+path = "examples/ruby/function_return_value.rs"
+required-features = ["ruby"]
+
+
 [dev-dependencies]
 tracing-subscriber = "0.3.18"
 mlua = { version = "0.9.8", features = ["luajit", "vendored", "send"] }

assets/examples/ruby/function_return_value.rb

@@ -0,0 +1,3 @@
+def get_value
+  42
+end

examples/ruby/function_return_value.rs

@@ -0,0 +1,42 @@
+use bevy::{app::AppExit, prelude::*};
+use bevy_scriptum::prelude::*;
+use bevy_scriptum::runtimes::ruby::prelude::*;
+use magnus::value::InnerValue;
+use magnus::TryConvert;
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_systems(Startup, startup)
+        .add_systems(Update, call_lua_on_update_from_rust)
+        .add_scripting::<RubyRuntime>(|runtime| {
+            runtime.add_function(String::from("quit"), |mut exit: EventWriter<AppExit>| {
+                exit.write(AppExit::Success);
+            });
+        })
+        .run();
+}
+
+fn startup(mut commands: Commands, assets_server: Res<AssetServer>) {
+    commands.spawn(Script::<RubyScript>::new(
+        assets_server.load("examples/ruby/function_return_value.rb"),
+    ));
+}
+
+fn call_lua_on_update_from_rust(
+    mut scripted_entities: Query<(Entity, &mut RubyScriptData)>,
+    scripting_runtime: ResMut<RubyRuntime>,
+    mut exit: EventWriter<AppExit>,
+) {
+    for (entity, mut script_data) in &mut scripted_entities {
+        let val = scripting_runtime
+            .call_fn("get_value", &mut script_data, entity, ())
+            .unwrap()
+            .0;
+        scripting_runtime.with_engine_thread(move |ruby| {
+            let val: i32 = TryConvert::try_convert(val.get_inner_with(&ruby)).unwrap();
+            println!("script returned: {}", val);
+        });
+        exit.write(AppExit::Success);
+    }
+}

src/runtimes/ruby.rs

@@ -275,7 +275,7 @@ impl Drop for RubyRuntime {
 }
 
 #[derive(Clone)]
-pub struct RubyValue(magnus::value::Opaque<magnus::Value>);
+pub struct RubyValue(pub magnus::value::Opaque<magnus::Value>);
 
 impl RubyValue {
     fn nil(ruby: &Ruby) -> Self {
@@ -339,11 +339,11 @@ impl Runtime for RubyRuntime {
     }
 
     fn with_engine_mut<T>(&mut self, _f: impl FnOnce(&mut Self::RawEngine) -> T) -> T {
-        unimplemented!();
+        unimplemented!("Ruby requires single threaded execution, use `with_engine_thread`");
     }
 
     fn with_engine<T>(&self, _f: impl FnOnce(&Self::RawEngine) -> T) -> T {
-        unimplemented!();
+        unimplemented!("Ruby requires single threaded execution, use `with_engine_thread`");
     }
 
     fn eval(