Struct bevy_ecs::query::QueryCombinationIter
source · pub struct QueryCombinationIter<'w, 's, D: QueryData, F: QueryFilter, const K: usize> { /* private fields */ }
Expand description
An iterator over K
-sized combinations of query items without repetition.
A combination is an arrangement of a collection of items where order does not matter.
K
is the number of items that make up each subset, and the number of items returned by the iterator.
N
is the number of total entities output by the query.
For example, given the list [1, 2, 3, 4], where K
is 2, the combinations without repeats are
[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4].
And in this case, N
would be defined as 4 since the size of the input list is 4.
The number of combinations depend on how K
relates to the number of entities matching the Query
:
- if
K = N
, only one combination exists, - if
K < N
, there are NCK combinations (see the performance section ofQuery
), - if
K > N
, there are no combinations.
The output combination is not guaranteed to have any order of iteration.
§Usage
This type is returned by calling Query::iter_combinations
or Query::iter_combinations_mut
.
It implements Iterator
only if it iterates over read-only query items (learn more).
In the case of mutable query items, it can be iterated by calling fetch_next
in a while let
loop.
§Examples
The following example shows how to traverse the iterator when the query items are read-only.
fn some_system(query: Query<&ComponentA>) {
for [a1, a2] in query.iter_combinations() {
// ...
}
}
The following example shows how fetch_next
should be called with a while let
loop to traverse the iterator when the query items are mutable.
fn some_system(mut query: Query<&mut ComponentA>) {
let mut combinations = query.iter_combinations_mut();
while let Some([a1, a2]) = combinations.fetch_next() {
// ...
}
}
Implementations§
source§impl<'w, 's, D: QueryData, F: QueryFilter, const K: usize> QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D: QueryData, F: QueryFilter, const K: usize> QueryCombinationIter<'w, 's, D, F, K>
sourcepub fn fetch_next(&mut self) -> Option<[D::Item<'_>; K]>
pub fn fetch_next(&mut self) -> Option<[D::Item<'_>; K]>
Get next combination of queried components
Trait Implementations§
source§impl<'w, 's, D: QueryData, F: QueryFilter, const K: usize> Debug for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D: QueryData, F: QueryFilter, const K: usize> Debug for QueryCombinationIter<'w, 's, D, F, K>
source§impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, const K: usize> Iterator for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, const K: usize> Iterator for QueryCombinationIter<'w, 's, D, F, K>
§type Item = [<D as WorldQuery>::Item<'w>; K]
type Item = [<D as WorldQuery>::Item<'w>; K]
source§fn next(&mut self) -> Option<Self::Item>
fn next(&mut self) -> Option<Self::Item>
source§fn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
source§fn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
fn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
iter_next_chunk
)N
values. Read more1.0.0 · source§fn count(self) -> usizewhere
Self: Sized,
fn count(self) -> usizewhere
Self: Sized,
1.0.0 · source§fn last(self) -> Option<Self::Item>where
Self: Sized,
fn last(self) -> Option<Self::Item>where
Self: Sized,
source§fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>
iter_advance_by
)n
elements. Read more1.0.0 · source§fn nth(&mut self, n: usize) -> Option<Self::Item>
fn nth(&mut self, n: usize) -> Option<Self::Item>
n
th element of the iterator. Read more1.28.0 · source§fn step_by(self, step: usize) -> StepBy<Self>where
Self: Sized,
fn step_by(self, step: usize) -> StepBy<Self>where
Self: Sized,
1.0.0 · source§fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>
fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>
1.0.0 · source§fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>where
Self: Sized,
U: IntoIterator,
fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>where
Self: Sized,
U: IntoIterator,
source§fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
iter_intersperse
)separator
between adjacent items of the original iterator. Read more1.0.0 · source§fn map<B, F>(self, f: F) -> Map<Self, F> ⓘ
fn map<B, F>(self, f: F) -> Map<Self, F> ⓘ
1.0.0 · source§fn filter<P>(self, predicate: P) -> Filter<Self, P>
fn filter<P>(self, predicate: P) -> Filter<Self, P>
1.0.0 · source§fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
1.0.0 · source§fn enumerate(self) -> Enumerate<Self>where
Self: Sized,
fn enumerate(self) -> Enumerate<Self>where
Self: Sized,
1.0.0 · source§fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
1.0.0 · source§fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
1.57.0 · source§fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>
1.0.0 · source§fn skip(self, n: usize) -> Skip<Self>where
Self: Sized,
fn skip(self, n: usize) -> Skip<Self>where
Self: Sized,
n
elements. Read more1.0.0 · source§fn take(self, n: usize) -> Take<Self>where
Self: Sized,
fn take(self, n: usize) -> Take<Self>where
Self: Sized,
n
elements, or fewer
if the underlying iterator ends sooner. Read more1.0.0 · source§fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
source§fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>
fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>
iter_map_windows
)f
for each contiguous window of size N
over
self
and returns an iterator over the outputs of f
. Like slice::windows()
,
the windows during mapping overlap as well. Read more1.0.0 · source§fn inspect<F>(self, f: F) -> Inspect<Self, F>
fn inspect<F>(self, f: F) -> Inspect<Self, F>
1.0.0 · source§fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
source§fn collect_into<E>(self, collection: &mut E) -> &mut E
fn collect_into<E>(self, collection: &mut E) -> &mut E
iter_collect_into
)1.0.0 · source§fn partition<B, F>(self, f: F) -> (B, B)
fn partition<B, F>(self, f: F) -> (B, B)
source§fn is_partitioned<P>(self, predicate: P) -> bool
fn is_partitioned<P>(self, predicate: P) -> bool
iter_is_partitioned
)true
precede all those that return false
. Read more1.27.0 · source§fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
1.27.0 · source§fn try_for_each<F, R>(&mut self, f: F) -> R
fn try_for_each<F, R>(&mut self, f: F) -> R
1.0.0 · source§fn fold<B, F>(self, init: B, f: F) -> B
fn fold<B, F>(self, init: B, f: F) -> B
1.51.0 · source§fn reduce<F>(self, f: F) -> Option<Self::Item>
fn reduce<F>(self, f: F) -> Option<Self::Item>
source§fn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
fn try_reduce<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
iterator_try_reduce
)1.0.0 · source§fn all<F>(&mut self, f: F) -> bool
fn all<F>(&mut self, f: F) -> bool
1.0.0 · source§fn any<F>(&mut self, f: F) -> bool
fn any<F>(&mut self, f: F) -> bool
1.0.0 · source§fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
1.30.0 · source§fn find_map<B, F>(&mut self, f: F) -> Option<B>
fn find_map<B, F>(&mut self, f: F) -> Option<B>
source§fn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
fn try_find<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
try_find
)1.0.0 · source§fn position<P>(&mut self, predicate: P) -> Option<usize>
fn position<P>(&mut self, predicate: P) -> Option<usize>
1.6.0 · source§fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn max_by<F>(self, compare: F) -> Option<Self::Item>
fn max_by<F>(self, compare: F) -> Option<Self::Item>
1.6.0 · source§fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn min_by<F>(self, compare: F) -> Option<Self::Item>
fn min_by<F>(self, compare: F) -> Option<Self::Item>
1.0.0 · source§fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
1.36.0 · source§fn copied<'a, T>(self) -> Copied<Self>
fn copied<'a, T>(self) -> Copied<Self>
source§fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>where
Self: Sized,
fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>where
Self: Sized,
iter_array_chunks
)N
elements of the iterator at a time. Read more1.11.0 · source§fn product<P>(self) -> P
fn product<P>(self) -> P
source§fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
iter_order_by
)Iterator
with those
of another with respect to the specified comparison function. Read more1.5.0 · source§fn partial_cmp<I>(self, other: I) -> Option<Ordering>
fn partial_cmp<I>(self, other: I) -> Option<Ordering>
PartialOrd
elements of
this Iterator
with those of another. The comparison works like short-circuit
evaluation, returning a result without comparing the remaining elements.
As soon as an order can be determined, the evaluation stops and a result is returned. Read moresource§fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
iter_order_by
)Iterator
with those
of another with respect to the specified comparison function. Read moresource§fn eq_by<I, F>(self, other: I, eq: F) -> bool
fn eq_by<I, F>(self, other: I, eq: F) -> bool
iter_order_by
)1.5.0 · source§fn lt<I>(self, other: I) -> bool
fn lt<I>(self, other: I) -> bool
Iterator
are lexicographically
less than those of another. Read more1.5.0 · source§fn le<I>(self, other: I) -> bool
fn le<I>(self, other: I) -> bool
Iterator
are lexicographically
less or equal to those of another. Read more1.5.0 · source§fn gt<I>(self, other: I) -> bool
fn gt<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than those of another. Read more1.5.0 · source§fn ge<I>(self, other: I) -> bool
fn ge<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than or equal to those of another. Read moresource§fn is_sorted_by<F>(self, compare: F) -> bool
fn is_sorted_by<F>(self, compare: F) -> bool
is_sorted
)source§fn is_sorted_by_key<F, K>(self, f: F) -> bool
fn is_sorted_by_key<F, K>(self, f: F) -> bool
is_sorted
)impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, const K: usize> FusedIterator for QueryCombinationIter<'w, 's, D, F, K>
Auto Trait Implementations§
impl<'w, 's, D, F, const K: usize> Freeze for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D, F, const K: usize> !RefUnwindSafe for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D, F, const K: usize> !Send for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D, F, const K: usize> !Sync for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D, F, const K: usize> Unpin for QueryCombinationIter<'w, 's, D, F, K>
impl<'w, 's, D, F, const K: usize> !UnwindSafe for QueryCombinationIter<'w, 's, D, F, K>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
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T: Any,
impl<T> Downcast for Twhere
T: Any,
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. This is needed since Rust cannot
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