Problems loading scene

[Nehliin]

Hello!

I have been trying out the scene loader and ran into some issues where no entities would be loaded at all. Here is a minimal example:

struct Player;
#[derive(Properties, Default)]
struct Enemy;
#[derive(Properties, Default)]
struct Health(u8);

fn test_world(mut commands: Commands) {
    commands
        .spawn(Camera2dComponents::default())
        .spawn((Player, Health(100)))
        .spawn((Enemy, Health(100)));
}

fn load_world(asset_server: Res<AssetServer>, mut scene_spawner: ResMut<SceneSpawner>) {
    let scene_handle: Handle<Scene> = asset_server.load("assets/scenes/start_scene.scn").unwrap();

    scene_spawner.load(scene_handle);
    println!("loaded");
    asset_server.watch_for_changes().unwrap();
}

fn print_system(mut query: Query<Entity>) {
    for entity in &mut query.iter() {
        println!("  Entity({})", entity.id());
    }
}

fn main() {
    App::build()
        .add_default_plugins()
        .register_component::<Health>()
        .register_component::<Player>()
        .register_component::<Enemy>()
        // This startup system is replaced with test_world the first time so the file can be saved
        .add_startup_system(load_world.system())
        .add_system(print_system.system())
        .run();
}

If I omit spawning the Camera2dComponents everything works as expected and the entities are spawned but if I leave it in I get no errors but no entities are actually loaded to the world. I was under the impression that I shouldn't have to register components that are "built in" to the engine. Is there something else I am missing? Here is the code I use to save the world (I use keyboard input to initiate the save logic but details are omitted):

fn save_scene(world: &mut World, resources: &mut Resources) {
    let type_registry = resources.get::<TypeRegistry>().unwrap();
    let scene = Scene::from_world(&world, &type_registry.component.read().unwrap());

    let mut file = File::create("assets/scenes/start_scene.scn").unwrap();
    file.write_all(
        scene
            .serialize_ron(&type_registry.property.read().unwrap())
            .unwrap()
            .as_bytes(),
    )
    .unwrap();
} 

[Moxinilian]

Sorry for the late reply! Would you mind telling me if you are still experiencing this issue with latest Bevy?

[martinfiers]

Regarding the saving part, this is related to #1442 , just posting it here as reference. See also https://discord.com/channels/691052431525675048/692648082499829760/838080584190132274 about a discussion on direct world access vs the solution proposed in 1442.

[MinerSebas]

Updating this to Bevy 0.5 everything works as expected:

use std::{fs::File, io::Write};

use bevy::prelude::*;
use bevy::reflect::*;

#[derive(Default, Reflect)]
#[reflect(Component)]
struct Player;
#[derive(Default, Reflect)]
#[reflect(Component)]
struct Enemy;
#[derive(Default, Reflect)]
#[reflect(Component)]
struct Health(u8);

fn test_world(mut commands: Commands) {
    commands.spawn_bundle(OrthographicCameraBundle::new_2d());
    commands.spawn_bundle((Player, Health(100)));
    commands.spawn_bundle((Enemy, Health(100)));
}

fn load_world(asset_server: Res<AssetServer>, mut scene_spawner: ResMut<SceneSpawner>) {
    let scene_handle: Handle<DynamicScene> = asset_server.load("scenes/start_scene.scn.ron");

    scene_spawner.spawn_dynamic(scene_handle);
    println!("loaded");
    asset_server.watch_for_changes().unwrap();
}

fn print_system(query: Query<Entity>) {
    for entity in &mut query.iter() {
        println!("  Entity({})", entity.id());
    }
}

fn save_scene(world: &mut World) {
    let type_registry = world.get_resource::<TypeRegistryArc>().unwrap();
    let scene = DynamicScene::from_world(&world, &type_registry);

    let mut file = File::create("assets/scenes/start_scene.scn.ron").unwrap();
    file.write_all(
        scene
            .serialize_ron(&type_registry)
            .unwrap()
            .as_bytes(),
    )
    .unwrap();
}

fn main() {
    App::build()
        .add_plugins(DefaultPlugins)
        .register_type::<Health>()
        .register_type::<Player>()
        .register_type::<Enemy>()
        // This startup system is replaced with test_world the first time so the file can be saved
        .add_startup_system(load_world.system())
        // Uncomment to create save file.
        //.add_startup_system(test_world.system())
        //.add_system(save_scene.exclusive_system().at_end())
        .add_system(print_system.system())
        .run();
}

[alice-i-cecile]

Closing as resolved <3