Struct bevy_ecs::query::QueryIter

pub struct QueryIter<'w, 's, D: QueryData, F: QueryFilter> { /* private fields */ }

An Iterator over query results of a Query.

This struct is created by the Query::iter and Query::iter_mut methods.

Implementations

impl<'w, 's, D: QueryData, F: QueryFilter> QueryIter<'w, 's, D, F>

pub fn sort<L: ReadOnlyQueryData + 'w>( self ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

where L::Item<'w>: Ord,

Sorts all query items into a new iterator, using the query lens as a key.

This sort is stable (i.e., does not reorder equal elements).

This uses slice::sort internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

Examples

// We can ensure that a query always returns in the same order.
fn system_1(query: Query<(Entity, &PartIndex)>) {
    let parts: Vec<(Entity, &PartIndex)> = query.iter().sort::<&PartIndex>().collect();
}

// We can freely rearrange query components in the key.
fn system_2(query: Query<(&Length, &Width, &Height), With<PartMarker>>) {
    for (length, width, height) in query.iter().sort::<(&Height, &Length, &Width)>() {
        println!("height: {height:?}, width: {width:?}, length: {length:?}")
    }
}

// We can sort by Entity without including it in the original Query.
// Here, we match iteration orders between query iterators.
fn system_3(
    part_query: Query<(&PartValue, &ParentEntity)>,
    mut parent_query: Query<(&ChildPartCount, &mut ParentValue)>,
) {
    let part_values = &mut part_query
        .into_iter()
        .sort::<&ParentEntity>()
        .map(|(&value, parent_entity)| *value);

    for (&child_count, mut parent_value) in parent_query.iter_mut().sort::<Entity>() {
        **parent_value = part_values.take(*child_count).sum();
    }
}

pub fn sort_unstable<L: ReadOnlyQueryData + 'w>( self ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

where L::Item<'w>: Ord,

Sorts all query items into a new iterator, using the query lens as a key.

This sort is unstable (i.e., may reorder equal elements).

This uses slice::sort_unstable internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes.. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

Example

#[derive(Component, PartialEq, Eq, PartialOrd, Ord)]
enum Flying {
    Enabled,
    Disabled
};

// We perform an unstable sort by a Component with few values.
fn system_1(query: Query<&Flying, With<PartMarker>>) {
    let part_values: Vec<&Flying> = query.iter().sort_unstable::<&Flying>().collect();
}

pub fn sort_by<L: ReadOnlyQueryData + 'w>( self, compare: impl FnMut(&L::Item<'w>, &L::Item<'w>) -> Ordering ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

Sorts all query items into a new iterator with a comparator function over the query lens.

This sort is stable (i.e., does not reorder equal elements).

This uses slice::sort_by internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

Example

#[derive(Component)]
struct PartValue(f32);

// We can use a cmp function on components do not implement Ord.
fn system_1(query: Query<&PartValue>) {
    // Sort part values according to `f32::total_comp`.
    let part_values: Vec<&PartValue> = query
        .iter()
        .sort_by::<&PartValue>(|value_1, value_2| value_1.total_cmp(*value_2))
        .collect();
}

pub fn sort_unstable_by<L: ReadOnlyQueryData + 'w>( self, compare: impl FnMut(&L::Item<'w>, &L::Item<'w>) -> Ordering ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

Sorts all query items into a new iterator with a comparator function over the query lens.

This sort is unstable (i.e., may reorder equal elements).

This uses slice::sort_unstable_by internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

pub fn sort_by_key<L: ReadOnlyQueryData + 'w, K>( self, f: impl FnMut(&L::Item<'w>) -> K ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

where K: Ord,

Sorts all query items into a new iterator with a key extraction function over the query lens.

This sort is stable (i.e., does not reorder equal elements).

This uses slice::sort_by_key internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

Example

#[derive(Component)]
struct AvailableMarker;

#[derive(Component, PartialEq, Eq, PartialOrd, Ord)]
enum Rarity {
  Common,
  Rare,
  Epic,
  Legendary
};

#[derive(Component)]
struct PartValue(f32);

// We can sort with the internals of components that do not implement Ord.
fn system_1(query: Query<(Entity, &PartValue)>) {
    // Sort by the sines of the part values.
    let parts: Vec<(Entity, &PartValue)> = query
        .iter()
        .sort_by_key::<&PartValue, _>(|value| value.sin() as usize)
        .collect();
}

// We can define our own custom comparison functions over an EntityRef.
fn system_2(query: Query<EntityRef, With<PartMarker>>) {
    // Sort by whether parts are available and their rarity.
    // We want the available legendaries to come first, so we reverse the iterator.
    let parts: Vec<EntityRef> = query.iter()
        .sort_by_key::<EntityRef, _>(|entity_ref| {
            (
                entity_ref.contains::<AvailableMarker>(),
                entity_ref.get::<Rarity>()
            )
        })
        .rev()
        .collect();
}

pub fn sort_unstable_by_key<L: ReadOnlyQueryData + 'w, K>( self, f: impl FnMut(&L::Item<'w>) -> K ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

where K: Ord,

Sorts all query items into a new iterator with a key extraction function over the query lens.

This sort is unstable (i.e., may reorder equal elements).

This uses slice::sort_unstable_by_key internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

pub fn sort_by_cached_key<L: ReadOnlyQueryData + 'w, K>( self, f: impl FnMut(&L::Item<'w>) -> K ) -> QuerySortedIter<'w, 's, D, F, impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w>

where K: Ord,

Sort all query items into a new iterator with a key extraction function over the query lens.

This sort is stable (i.e., does not reorder equal elements).

This uses slice::sort_by_cached_key internally.

Defining the lens works like transmute_lens. This includes the allowed parameter type changes listed under allowed transmutes. However, the lens uses the filter of the original query when present.

The sort is not cached across system runs.

Panics

This will panic if next has been called on QueryIter before, unless the underlying Query is empty.

Trait Implementations

impl<'w, 's, D: QueryData, F: QueryFilter> Debug for QueryIter<'w, 's, D, F>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'w, 's, D: QueryData, F> ExactSizeIterator for QueryIter<'w, 's, D, F>

where F: ArchetypeFilter + QueryFilter,

fn len(&self) -> usize

Returns the exact remaining length of the iterator.

fn is_empty(&self) -> bool

🔬This is a nightly-only experimental API. (exact_size_is_empty)

Returns true if the iterator is empty.

impl<'w, 's, D: QueryData, F: QueryFilter> Iterator for QueryIter<'w, 's, D, F>

type Item = <D as WorldQuery>::Item<'w>

The type of the elements being iterated over.

fn next(&mut self) -> Option<Self::Item>

Advances the iterator and returns the next value.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

fn fold<B, Func>(self, init: B, func: Func) -> B

where Func: FnMut(B, Self::Item) -> B,

Folds every element into an accumulator by applying an operation, returning the final result.

fn next_chunk<const N: usize>( &mut self ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk)

Advances the iterator and returns an array containing the next N values.

fn count(self) -> usize

where Self: Sized,

Consumes the iterator, counting the number of iterations and returning it.

fn last(self) -> Option<Self::Item>

where Self: Sized,

Consumes the iterator, returning the last element.

fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by)

Advances the iterator by n elements.

fn nth(&mut self, n: usize) -> Option<Self::Item>

Returns the nth element of the iterator.

fn step_by(self, step: usize) -> StepBy<Self>

where Self: Sized,

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator<Item = Self::Item>,

Takes two iterators and creates a new iterator over both in sequence.

fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator,

‘Zips up’ two iterators into a single iterator of pairs.

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>

where Self: Sized, G: FnMut() -> Self::Item,

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator.

fn map<B, F>(self, f: F) -> Map<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates an iterator which calls that closure on each element.

fn for_each<F>(self, f: F)

where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each element of an iterator.

fn filter<P>(self, predicate: P) -> Filter<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator which uses a closure to determine if an element should be yielded.

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both filters and maps.

fn enumerate(self) -> Enumerate<Self>

where Self: Sized,

Creates an iterator which gives the current iteration count as well as the next value.

fn peekable(self) -> Peekable<Self>

where Self: Sized,

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information.

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that skips elements based on a predicate.

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that yields elements based on a predicate.

fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>

where Self: Sized, P: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both yields elements based on a predicate and maps.

fn skip(self, n: usize) -> Skip<Self>

where Self: Sized,

Creates an iterator that skips the first n elements.

fn take(self, n: usize) -> Take<Self>

where Self: Sized,

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner.

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>

where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

An iterator adapter which, like fold, holds internal state, but unlike fold, produces a new iterator.

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>

where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,

Creates an iterator that works like map, but flattens nested structure.

fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>

where Self: Sized, F: FnMut(&[Self::Item; N]) -> R,

🔬This is a nightly-only experimental API. (iter_map_windows)

Calls the given function 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.

fn fuse(self) -> Fuse<Self>

where Self: Sized,

Creates an iterator which ends after the first None.

fn inspect<F>(self, f: F) -> Inspect<Self, F>

where Self: Sized, F: FnMut(&Self::Item),

Does something with each element of an iterator, passing the value on.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Borrows an iterator, rather than consuming it.

fn collect<B>(self) -> B

where B: FromIterator<Self::Item>, Self: Sized,

Transforms an iterator into a collection.

fn collect_into<E>(self, collection: &mut E) -> &mut E

where E: Extend<Self::Item>, Self: Sized,

🔬This is a nightly-only experimental API. (iter_collect_into)

Collects all the items from an iterator into a collection.

fn partition<B, F>(self, f: F) -> (B, B)

where Self: Sized, B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool,

Consumes an iterator, creating two collections from it.

fn is_partitioned<P>(self, predicate: P) -> bool

where Self: Sized, P: FnMut(Self::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_is_partitioned)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false.

fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R

where Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Output = B>,

An iterator method that applies a function as long as it returns successfully, producing a single, final value.

fn try_for_each<F, R>(&mut self, f: F) -> R

where Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Output = ()>,

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error.

fn reduce<F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Self::Item,

Reduces the elements to a single one, by repeatedly applying a reducing operation.

fn try_reduce<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType

where Self: Sized, F: FnMut(Self::Item, Self::Item) -> R, R: Try<Output = Self::Item>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (iterator_try_reduce)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately.

fn all<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the iterator matches a predicate.

fn any<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the iterator matches a predicate.

fn find<P>(&mut self, predicate: P) -> Option<Self::Item>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator that satisfies a predicate.

fn find_map<B, F>(&mut self, f: F) -> Option<B>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Applies function to the elements of iterator and returns the first non-none result.

fn try_find<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType

where Self: Sized, F: FnMut(&Self::Item) -> R, R: Try<Output = bool>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (try_find)

Applies function to the elements of iterator and returns the first true result or the first error.

fn position<P>(&mut self, predicate: P) -> Option<usize>

where Self: Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in an iterator, returning its index.

fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value from the specified function.

fn max_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function.

fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value from the specified function.

fn min_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function.

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)

where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Sized + Iterator<Item = (A, B)>,

Converts an iterator of pairs into a pair of containers.

fn copied<'a, T>(self) -> Copied<Self>

where T: 'a + Copy, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which copies all of its elements.

fn cloned<'a, T>(self) -> Cloned<Self>

where T: 'a + Clone, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which clones all of its elements.

fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_array_chunks)

Returns an iterator over N elements of the iterator at a time.

fn sum<S>(self) -> S

where Self: Sized, S: Sum<Self::Item>,

Sums the elements of an iterator.

fn product<P>(self) -> P

where Self: Sized, P: Product<Self::Item>,

Iterates over the entire iterator, multiplying all the elements

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn partial_cmp<I>(self, other: I) -> Option<Ordering>

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Lexicographically compares the 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.

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>,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn eq<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are equal to those of another.

fn eq_by<I, F>(self, other: I, eq: F) -> bool

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_order_by)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function.

fn ne<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are not equal to those of another.

fn lt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less than those of another.

fn le<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

fn gt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than those of another.

fn ge<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

fn is_sorted_by<F>(self, compare: F) -> bool

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> bool,

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this iterator are sorted using the given comparator function.

fn is_sorted_by_key<F, K>(self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> K, K: PartialOrd,

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this iterator are sorted using the given key extraction function.

impl<'w, 's, D: QueryData, F: QueryFilter> FusedIterator for QueryIter<'w, 's, D, F>