ba5e71f53d
Fixes #17412 ## Objective `Parent` uses the "has a X" naming convention. There is increasing sentiment that we should use the "is a X" naming convention for relationships (following #17398). This leaves `Children` as-is because there is prevailing sentiment that `Children` is clearer than `ParentOf` in many cases (especially when treating it like a collection). This renames `Parent` to `ChildOf`. This is just the implementation PR. To discuss the path forward, do so in #17412. ## Migration Guide - The `Parent` component has been renamed to `ChildOf`.
113 lines
3.5 KiB
Markdown
113 lines
3.5 KiB
Markdown
# B0004
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A runtime warning.
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An [`Entity`] with a hierarchy-inherited component has a [`ChildOf`]
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without the hierarchy-inherited component in question.
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The hierarchy-inherited components defined in bevy include:
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- [`InheritedVisibility`]
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- [`GlobalTransform`]
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Third party plugins may also define their own hierarchy components, so
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read the warning message carefully and pay attention to the exact type
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of the missing component.
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To fix this warning, add the missing hierarchy component to all ancestors
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of entities with the hierarchy component you wish to use.
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The following code will cause a warning to be emitted:
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```rust,no_run
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use bevy::prelude::*;
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// WARNING: this code is buggy
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fn setup_cube(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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commands
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.spawn(Transform::default())
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.with_children(|parent| {
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// cube
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parent.spawn((
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Mesh3d(meshes.add(Cuboid::default())),
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MeshMaterial3d(materials.add(Color::srgb(0.8, 0.7, 0.6))),
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Transform::from_xyz(0.0, 0.5, 0.0),
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));
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});
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// camera
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
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));
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_systems(Startup, setup_cube)
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.run();
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}
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```
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This code **will not** show a cube on screen.
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This is because the entity spawned with `commands.spawn(…)`
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doesn't have a [`ViewVisibility`] or [`InheritedVisibility`] component.
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Since the cube is spawned as a child of an entity without the
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visibility components, it will not be visible at all.
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To fix this, you must also add a [`Visibility`] component.
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It automatically adds the other relevant visibility components for you:
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```rust,no_run
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use bevy::prelude::*;
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fn setup_cube(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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commands
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.spawn((Transform::default(), Visibility::default()))
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.with_children(|parent| {
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// cube
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parent.spawn((
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Mesh3d(meshes.add(Cuboid::default())),
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MeshMaterial3d(materials.add(Color::srgb(0.8, 0.7, 0.6))),
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Transform::from_xyz(0.0, 0.5, 0.0),
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));
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});
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// camera
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
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));
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_systems(Startup, setup_cube)
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.run();
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}
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```
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A similar problem occurs when the [`GlobalTransform`] component is missing.
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However, it will be automatically inserted whenever `Transform` is
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inserted, as it is a required component.
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You will most likely encounter this warning when loading a scene
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as a child of a pre-existing [`Entity`] that does not have the proper components.
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[`InheritedVisibility`]: https://docs.rs/bevy/*/bevy/render/view/struct.InheritedVisibility.html
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[`ViewVisibility`]: https://docs.rs/bevy/*/bevy/render/view/struct.ViewVisibility.html
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[`Visibility`]: https://docs.rs/bevy/*/bevy/render/view/struct.Visibility.html
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[`GlobalTransform`]: https://docs.rs/bevy/*/bevy/transform/components/struct.GlobalTransform.html
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[`ChildOf`]: https://docs.rs/bevy/*/bevy/ecs/hierarchy/struct.ChildOf.html
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[`Entity`]: https://docs.rs/bevy/*/bevy/ecs/entity/struct.Entity.html
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