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Support returning data out of with_children (#4708)
# Objective Support returning data out of with_children to enable the use case of changing the parent commands with data created inside the child builder. ## Solution Change the with_children closure to return T. Closes https://github.com/bevyengine/bevy/pull/2817. --- ## Changelog `BuildChildren::add_children` was added with the ability to return data to use outside the closure (for spawning a new child builder on a returned entity for example).
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1 changed files with 65 additions and 22 deletions
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@ -1,11 +1,13 @@
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use crate::prelude::{Children, Parent, PreviousParent};
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use smallvec::SmallVec;
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use bevy_ecs::{
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bundle::Bundle,
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entity::Entity,
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system::{Command, Commands, EntityCommands},
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world::{EntityMut, World},
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};
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use smallvec::SmallVec;
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use crate::prelude::{Children, Parent, PreviousParent};
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/// Command that adds a child to an entity
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#[derive(Debug)]
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@ -165,7 +167,40 @@ impl<'w, 's, 'a> ChildBuilder<'w, 's, 'a> {
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/// Trait defining how to build children
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pub trait BuildChildren {
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/// Creates a [`ChildBuilder`] with the given children built in the given closure
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///
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/// Compared to [`add_children`][BuildChildren::add_children], this method returns self
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/// to allow chaining.
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fn with_children(&mut self, f: impl FnOnce(&mut ChildBuilder)) -> &mut Self;
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/// Creates a [`ChildBuilder`] with the given children built in the given closure
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///
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/// Compared to [`with_children`][BuildChildren::with_children], this method returns the
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/// the value returned from the closure, but doesn't allow chaining.
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///
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/// ## Example
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///
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/// ```no_run
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/// # use bevy_ecs::prelude::*;
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/// # use bevy_hierarchy::*;
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/// #
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/// # #[derive(Component)]
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/// # struct SomethingElse;
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/// #
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/// # #[derive(Component)]
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/// # struct MoreStuff;
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/// #
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/// # fn foo(mut commands: Commands) {
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/// let mut parent_commands = commands.spawn();
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/// let child_id = parent_commands.add_children(|parent| {
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/// parent.spawn().id()
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/// });
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///
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/// parent_commands.insert(SomethingElse);
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/// commands.entity(child_id).with_children(|parent| {
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/// parent.spawn().insert(MoreStuff);
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/// });
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/// # }
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/// ```
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fn add_children<T>(&mut self, f: impl FnOnce(&mut ChildBuilder) -> T) -> T;
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/// Pushes children to the back of the builder's children
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fn push_children(&mut self, children: &[Entity]) -> &mut Self;
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/// Inserts children at the given index
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@ -178,8 +213,12 @@ pub trait BuildChildren {
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impl<'w, 's, 'a> BuildChildren for EntityCommands<'w, 's, 'a> {
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fn with_children(&mut self, spawn_children: impl FnOnce(&mut ChildBuilder)) -> &mut Self {
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self.add_children(spawn_children);
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self
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}
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fn add_children<T>(&mut self, spawn_children: impl FnOnce(&mut ChildBuilder) -> T) -> T {
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let parent = self.id();
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let push_children = {
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let mut builder = ChildBuilder {
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commands: self.commands(),
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push_children: PushChildren {
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@ -187,12 +226,12 @@ impl<'w, 's, 'a> BuildChildren for EntityCommands<'w, 's, 'a> {
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parent,
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},
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};
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spawn_children(&mut builder);
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builder.push_children
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};
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self.commands().add(push_children);
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self
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let result = spawn_children(&mut builder);
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let children = builder.push_children;
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self.commands().add(children);
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result
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}
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fn push_children(&mut self, children: &[Entity]) -> &mut Self {
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@ -460,15 +499,18 @@ impl<'w> BuildWorldChildren for WorldChildBuilder<'w> {
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#[cfg(test)]
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mod tests {
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use super::{BuildChildren, BuildWorldChildren};
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use crate::prelude::{Children, Parent, PreviousParent};
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use smallvec::{smallvec, SmallVec};
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use bevy_ecs::{
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component::Component,
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entity::Entity,
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system::{CommandQueue, Commands},
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world::World,
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};
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use smallvec::{smallvec, SmallVec};
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use crate::prelude::{Children, Parent, PreviousParent};
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use super::{BuildChildren, BuildWorldChildren};
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#[derive(Component)]
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struct C(u32);
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@ -479,12 +521,13 @@ mod tests {
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let mut queue = CommandQueue::default();
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let mut commands = Commands::new(&mut queue, &world);
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let mut children = Vec::new();
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let parent = commands.spawn().insert(C(1)).id();
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commands.entity(parent).with_children(|parent| {
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children.push(parent.spawn().insert(C(2)).id());
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children.push(parent.spawn().insert(C(3)).id());
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children.push(parent.spawn().insert(C(4)).id());
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let children = commands.entity(parent).add_children(|parent| {
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[
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parent.spawn().insert(C(2)).id(),
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parent.spawn().insert(C(3)).id(),
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parent.spawn().insert(C(4)).id(),
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]
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});
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queue.apply(&mut world);
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