bevy_ecs/world/
spawn_batch.rs

1use crate::{
2    bundle::{Bundle, BundleSpawner, NoBundleEffect},
3    change_detection::MaybeLocation,
4    entity::{Entity, EntitySetIterator},
5    world::World,
6};
7use core::iter::FusedIterator;
8
9/// An iterator that spawns a series of entities and returns the [ID](Entity) of
10/// each spawned entity.
11///
12/// If this iterator is not fully exhausted, any remaining entities will be spawned when this type is dropped.
13pub struct SpawnBatchIter<'w, I>
14where
15    I: Iterator,
16    I::Item: Bundle,
17{
18    inner: I,
19    spawner: BundleSpawner<'w>,
20    caller: MaybeLocation,
21}
22
23impl<'w, I> SpawnBatchIter<'w, I>
24where
25    I: Iterator,
26    I::Item: Bundle<Effect: NoBundleEffect>,
27{
28    #[inline]
29    #[track_caller]
30    pub(crate) fn new(world: &'w mut World, iter: I, caller: MaybeLocation) -> Self {
31        // Ensure all entity allocations are accounted for so `self.entities` can realloc if
32        // necessary
33        world.flush();
34
35        let change_tick = world.change_tick();
36
37        let (lower, upper) = iter.size_hint();
38        let length = upper.unwrap_or(lower);
39        world.entities.reserve(length as u32);
40
41        let mut spawner = BundleSpawner::new::<I::Item>(world, change_tick);
42        spawner.reserve_storage(length);
43
44        Self {
45            inner: iter,
46            spawner,
47            caller,
48        }
49    }
50}
51
52impl<I> Drop for SpawnBatchIter<'_, I>
53where
54    I: Iterator,
55    I::Item: Bundle,
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,
70{
71    type Item = Entity;
72
73    fn next(&mut self) -> Option<Entity> {
74        let bundle = self.inner.next()?;
75        // SAFETY: bundle matches spawner type
76        unsafe { Some(self.spawner.spawn(bundle, self.caller).0) }
77    }
78
79    fn size_hint(&self) -> (usize, Option<usize>) {
80        self.inner.size_hint()
81    }
82}
83
84impl<I, T> ExactSizeIterator for SpawnBatchIter<'_, I>
85where
86    I: ExactSizeIterator<Item = T>,
87    T: Bundle,
88{
89    fn len(&self) -> usize {
90        self.inner.len()
91    }
92}
93
94impl<I, T> FusedIterator for SpawnBatchIter<'_, I>
95where
96    I: FusedIterator<Item = T>,
97    T: Bundle,
98{
99}
100
101// SAFETY: Newly spawned entities are unique.
102unsafe impl<I: Iterator, T> EntitySetIterator for SpawnBatchIter<'_, I>
103where
104    I: FusedIterator<Item = T>,
105    T: Bundle,
106{
107}
bevy_ecs/world/spawn_batch.rs

bevy_ecs/world/
spawn_batch.rs
