bevy_ecs/world/
spawn_batch.rs

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

bevy_ecs/world/
spawn_batch.rs
