bevy_ecs/world/
spawn_batch.rs

1use bevy_ptr::move_as_ptr;
2
3use crate::{
4    bundle::{Bundle, BundleSpawner, NoBundleEffect},
5    change_detection::MaybeLocation,
6    entity::{AllocEntitiesIterator, Entity, EntitySetIterator},
7    world::World,
8};
9use core::iter::FusedIterator;
10
11/// An iterator that spawns a series of entities and returns the [ID](Entity) of
12/// each spawned entity.
13///
14/// If this iterator is not fully exhausted, any remaining entities will be spawned when this type is dropped.
15pub struct SpawnBatchIter<'w, I>
16where
17    I: Iterator,
18    I::Item: Bundle<Effect: NoBundleEffect>,
19{
20    inner: I,
21    spawner: BundleSpawner<'w>,
22    allocator: AllocEntitiesIterator<'w>,
23    caller: MaybeLocation,
24}
25
26impl<'w, I> SpawnBatchIter<'w, I>
27where
28    I: Iterator,
29    I::Item: Bundle<Effect: NoBundleEffect>,
30{
31    #[inline]
32    #[track_caller]
33    pub(crate) fn new(world: &'w mut World, iter: I, caller: MaybeLocation) -> Self {
34        let change_tick = world.change_tick();
35
36        let (lower, upper) = iter.size_hint();
37        let length = upper.unwrap_or(lower);
38
39        let mut spawner = BundleSpawner::new::<I::Item>(world, change_tick);
40        spawner.reserve_storage(length);
41        let allocator = spawner.allocator().alloc_many(length as u32);
42
43        Self {
44            inner: iter,
45            allocator,
46            spawner,
47            caller,
48        }
49    }
50}
51
52impl<I> Drop for SpawnBatchIter<'_, I>
53where
54    I: Iterator,
55    I::Item: Bundle<Effect: NoBundleEffect>,
56{
57    fn drop(&mut self) {
58        // Iterate through self in order to spawn remaining bundles.
59        for _ in &mut *self {}
60        // Apply any commands from those operations.
61        // SAFETY: `self.spawner` will be dropped immediately after this call.
62        unsafe { self.spawner.flush_commands() };
63    }
64}
65
66impl<I> Iterator for SpawnBatchIter<'_, I>
67where
68    I: Iterator,
69    I::Item: Bundle<Effect: NoBundleEffect>,
70{
71    type Item = Entity;
72
73    fn next(&mut self) -> Option<Entity> {
74        let bundle = self.inner.next()?;
75        move_as_ptr!(bundle);
76        Some(if let Some(bulk) = self.allocator.next() {
77            // SAFETY: bundle matches spawner type and we just allocated it
78            unsafe {
79                self.spawner.spawn_at(bulk, bundle, self.caller);
80            }
81            bulk
82        } else {
83            // SAFETY: bundle matches spawner type
84            unsafe { self.spawner.spawn(bundle, self.caller) }
85        })
86    }
87
88    fn size_hint(&self) -> (usize, Option<usize>) {
89        self.inner.size_hint()
90    }
91}
92
93impl<I, T> ExactSizeIterator for SpawnBatchIter<'_, I>
94where
95    I: ExactSizeIterator<Item = T>,
96    T: Bundle<Effect: NoBundleEffect>,
97{
98    fn len(&self) -> usize {
99        self.inner.len()
100    }
101}
102
103impl<I, T> FusedIterator for SpawnBatchIter<'_, I>
104where
105    I: FusedIterator<Item = T>,
106    T: Bundle<Effect: NoBundleEffect>,
107{
108}
109
110// SAFETY: Newly spawned entities are unique.
111unsafe impl<I: Iterator, T> EntitySetIterator for SpawnBatchIter<'_, I>
112where
113    I: FusedIterator<Item = T>,
114    T: Bundle<Effect: NoBundleEffect>,
115{
116}
bevy_ecs/world/spawn_batch.rs

bevy_ecs/world/
spawn_batch.rs
