Best way to expose a getter/setter for a component of a child of an entity?

[elenakrittik]

Sorry for a cumbersome title.

I have a TextInput component that's designed to be used as a UI entity/node. To display the text i use bevy's builtin Text UI node and for technical reasons it needs to be nested in a few parent/child layers below TextInput instead of it and TextInput existing side-by-side on the same entity. A visual may be easier to understand:

- TextInput (what the user will use to create a text input field)
  - (internal/private nodes the user shouldn't know or care about)
    - Text (the node/entity/component responsible for storing and displaying the text `String`)

What would be the best way to expose a getter/setter for Text.0 (the text String) in a way that doesn't require the user of a TextInput to query and/or know about any of the "intermediate", private nodes?

[jfouche]

I suppose there are multiple solution. Here is a solution I often use (something like) :

#[derive(Component)]
pub struct TextInput {
   pub content: String,
}

#[derive(Component)]
struct TextInputTag;

fn create_text_input(
   trigger: Trigger<OnAdd, TextInput>, 
   mut commands: Commands, inputs: Query<&TextInput>
) {
   let input = inputs.get(trigger.entity()).unwrap();
   commands.entity(trigger.entity()).with_children(|parent| {
      parent.spawn(...);
      parent.spawn((Text(input.content.clone()), TextInputTag));
      parent.spawn(...);
   });
}

fn update_text(
   inputs: Query<&TextInput, Changed<TextInput>>, 
   mut texts: Query<(&mut Text, &Parent), With<TextInputTag>>
) {
   for (mut text, parent) in &mut texts {
      if let Ok(input) = inputs.get(**parent) {
         text.0 = input.content.clone();
      }
   }
}

pub struct InputTextPlugin;

impl Plugin for InputTextPlugin {
   fn build(app: &mut App) {
      app.add_system(Update, update_text).observe(create_text_input);
   }
}

[elenakrittik]

Yeah, i'm afraid that's exactly what i was trying to avoid (copying the content string). Thanks anyway (and sorry for the late reply)!

[Henauxg]

If I understand your question correctly, you're more interested in a way to hide your custom Entity hierarchy between your two text entities ?

You could have a look at the upcoming entity relationships coming in the soon to be released version 0.16.0 (#17398).

Or you could just DIY store a component on your TextInput entity storing a reference to the Text display entity, something like:

#[derive(Component)]
struct TextRef(pub Entity);

This way your hierarchy does not matter and can freely change without breaking any user-side code. You just query the TextRef component and access the Text component of the referenced entity.

[elenakrittik]

Oh, thanks... now i feel dumb 😅 Storing the Text's Entity is definitely an option, and i will look into the new relationship system once bevy 0.16 releases. Thanks again!