How to get all components for a specific entity?

[MrGVSV]

Asking and answering this for other users' who might have the same question

Is there a way to print a list of all components on an entity for debugging purposes?

[MrGVSV]

Here's a helper function for collecting the ComponentId for an entity's archetype:

pub fn get_components_for_entity<'a>(
    entity: &Entity,
    archetypes: &'a Archetypes,
) -> Option<impl Iterator<Item = ComponentId> + 'a> {
    for archetype in archetypes.iter() {
        if archetype.entities().contains(entity) {
            return Some(archetype.components());
        }
    }
    None
}

And you can use it like this:

// The system to print the components
pub fn my_system(archetypes: &Archetypes, components: &Components, /** ... */) {

  // ...

  for comp_id in get_components_for_entity(&my_entity, archetypes).unwrap() {
    if let Some(comp_info) = components.get_info(comp_id) {
      println!("Component: {:?}", comp_info);
    }
  }
}

[OriginLive]

Doesn't work with bevy 0.9 :(

[kristoff3r]

Doesn't work with bevy 0.9 :(

In bevy 0.9 you can replace

if archetype.entities().contains(entity) {

With

if archetype.entities().iter().any(|e| e.entity() == entity) {

[mrchantey]

Here's a modification that I use:

pub fn all_component_ids<'a>(
    world: &'a World,
    entity: Entity,
) -> impl Iterator<Item = ComponentId> + 'a {
    let components = world.components();
    for archetype in world.archetypes().iter() {
        if archetype.entities().iter().any(|e| e.entity() == entity) {
            return archetype.components();
        }
    }
    world.archetypes().empty().components()
}
pub fn all_component_infos<'a>(
    world: &'a World,
    entity: Entity,
) -> impl Iterator<Item = &'a ComponentInfo> + 'a {
    let components = world.components();
    all_component_ids(world, entity).map(|id| {
        components
            .get_info(id)
            .expect("Component id without info, this shouldnt happen..")
    })
}

Usage:

let names = all_component_infos(&app.world, entity)
        .map(|info| info.name())
        .collect::<Vec<_>>()
        .join("\n\n");
println!("{names}");

[MrGVSV]

Thanks for this! I think we can simplify even further though! I just posted a new answer here 😄

[mrchantey]

Awesome thanks for updating this!

[MrGVSV]

Update: This can be done a lot simpler now with just a World reference using World::inspect_entity.

fn my_system(world: &World) {
  // ...

  println!("{:#?}", world.inspect_entity(my_entity));
}

I believe this method was added in v0.9, whereas my original answer was likely from v0.5.

[cstegel]

Thanks for the tip about World::inspect_entity! To build on this in case others find it (like I did), the debug printing of ComponentInfo is extremely verbose so it might be good to start with just the names. Also, it needs to be collected into a Vec to be printed:

fn my_system(world: &World) {
  // ...

  println!("{:#?}", world.inspect_entity(my_entity)
                         .map(|info| info.name())
                         .collect::<Vec<_>>());
}