Struct bevy::prelude::QueryState

pub struct QueryState<Q, F = ()> where
    Q: WorldQuery,
    F: WorldQuery,
    <F as WorldQuery>::Fetch: FilterFetch,  { /* private fields */ }

Provides scoped access to a World state according to a given WorldQuery and query filter.

Implementations

impl<Q, F> QueryState<Q, F> where
    Q: WorldQuery,
    F: WorldQuery,
    <F as WorldQuery>::Fetch: FilterFetch, 

pub fn new(world: &mut World) -> QueryState<Q, F>

Creates a new QueryState from a given World and inherits the result of world.id().

pub fn is_empty(
    &self,
    world: &World,
    last_change_tick: u32,
    change_tick: u32
) -> bool

Checks if the query is empty for the given World, where the last change and current tick are given.

pub fn update_archetypes(&mut self, world: &World)

Takes a query for the given World, checks if the given world is the same as the query, and generates new archetypes for the given world.

Panics

Panics if the world.id() does not equal the current QueryState internal id.

pub fn validate_world(&self, world: &World)

pub fn new_archetype(&mut self, archetype: &Archetype)

Creates a new Archetype.

pub fn get(
    &'s mut self,
    world: &'w World,
    entity: Entity
) -> Result<<<Q as WorldQuery>::ReadOnlyFetch as Fetch<'w, 's>>::Item, QueryEntityError>

Gets the query result for the given World and Entity.

This can only be called for read-only queries, see Self::get_mut for write-queries.

pub fn get_many<const N: usize>(
    &'s mut self,
    world: &'w World,
    entities: [Entity; N]
) -> Result<[<<Q as WorldQuery>::ReadOnlyFetch as Fetch<'w, 's>>::Item; N], QueryEntityError>

Returns the read-only query results for the given array of Entity.

In case of a nonexisting entity or mismatched component, a QueryEntityError is returned instead.

Note that the unlike QueryState::get_many_mut, the entities passed in do not need to be unique.

Examples

use bevy_ecs::prelude::*;
use bevy_ecs::query::QueryEntityError;

#[derive(Component, PartialEq, Debug)]
struct A(usize);

let mut world = World::new();
let entity_vec: Vec<Entity> = (0..3).map(|i|world.spawn().insert(A(i)).id()).collect();
let entities: [Entity; 3] = entity_vec.try_into().unwrap();

world.spawn().insert(A(73));

let mut query_state = world.query::<&A>();

let component_values = query_state.get_many(&world, entities).unwrap();

assert_eq!(component_values, [&A(0), &A(1), &A(2)]);

let wrong_entity = Entity::from_raw(365);

assert_eq!(query_state.get_many(&world, [wrong_entity]), Err(QueryEntityError::NoSuchEntity(wrong_entity)));

pub fn get_mut(
    &'s mut self,
    world: &'w mut World,
    entity: Entity
) -> Result<<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item, QueryEntityError>

Gets the query result for the given World and Entity.

pub fn get_many_mut<const N: usize>(
    &'s mut self,
    world: &'w mut World,
    entities: [Entity; N]
) -> Result<[<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item; N], QueryEntityError>

Returns the query results for the given array of Entity.

In case of a nonexisting entity or mismatched component, a QueryEntityError is returned instead.

use bevy_ecs::prelude::*;
use bevy_ecs::query::QueryEntityError;

#[derive(Component, PartialEq, Debug)]
struct A(usize);

let mut world = World::new();

let entities: Vec<Entity> = (0..3).map(|i|world.spawn().insert(A(i)).id()).collect();
let entities: [Entity; 3] = entities.try_into().unwrap();

world.spawn().insert(A(73));

let mut query_state = world.query::<&mut A>();

let mut mutable_component_values = query_state.get_many_mut(&mut world, entities).unwrap();

for mut a in mutable_component_values.iter_mut(){
    a.0 += 5;
}

let component_values = query_state.get_many(&world, entities).unwrap();

assert_eq!(component_values, [&A(5), &A(6), &A(7)]);

let wrong_entity = Entity::from_raw(57);
let invalid_entity = world.spawn().id();

assert_eq!(query_state.get_many_mut(&mut world, [wrong_entity]).unwrap_err(), QueryEntityError::NoSuchEntity(wrong_entity));
assert_eq!(query_state.get_many_mut(&mut world, [invalid_entity]).unwrap_err(), QueryEntityError::QueryDoesNotMatch(invalid_entity));
assert_eq!(query_state.get_many_mut(&mut world, [entities[0], entities[0]]).unwrap_err(), QueryEntityError::AliasedMutability(entities[0]));

pub fn get_manual(
    &'s self,
    world: &'w World,
    entity: Entity
) -> Result<<<Q as WorldQuery>::ReadOnlyFetch as Fetch<'w, 's>>::Item, QueryEntityError>

pub unsafe fn get_unchecked(
    &'s mut self,
    world: &'w World,
    entity: Entity
) -> Result<<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item, QueryEntityError>

Gets the query result for the given World and Entity.

Safety

This does not check for mutable query correctness. To be safe, make sure mutable queries have unique access to the components they query.

pub fn iter(
    &'s mut self,
    world: &'w World
) -> QueryIter<'w, 's, Q, <Q as WorldQuery>::ReadOnlyFetch, F>

Returns an Iterator over the query results for the given World.

This can only be called for read-only queries, see Self::iter_mut for write-queries.

pub fn iter_mut(
    &'s mut self,
    world: &'w mut World
) -> QueryIter<'w, 's, Q, <Q as WorldQuery>::Fetch, F>

Returns an Iterator over the query results for the given World.

pub fn iter_manual(
    &'s self,
    world: &'w World
) -> QueryIter<'w, 's, Q, <Q as WorldQuery>::ReadOnlyFetch, F>

Returns an Iterator over the query results for the given World without updating the query’s archetypes. Archetypes must be manually updated before by using Self::update_archetypes.

This can only be called for read-only queries.

pub fn iter_combinations<const K: usize>(
    &'s mut self,
    world: &'w World
) -> QueryCombinationIter<'w, 's, Q, <Q as WorldQuery>::ReadOnlyFetch, F, K>

Returns an Iterator over all possible combinations of K query results without repetition. This can only be called for read-only queries.

For permutations of size K of query returning N results, you will get:

• if K == N: one permutation of all query results
• if K < N: all possible K-sized combinations of query results, without repetition
• if K > N: empty set (no K-sized combinations exist)

This can only be called for read-only queries, see Self::iter_combinations_mut for write-queries.

pub fn iter_combinations_mut<const K: usize>(
    &'s mut self,
    world: &'w mut World
) -> QueryCombinationIter<'w, 's, Q, <Q as WorldQuery>::Fetch, F, K>

Iterates over all possible combinations of K query results for the given World without repetition.

For permutations of size K of query returning N results, you will get:

• if K == N: one permutation of all query results
• if K < N: all possible K-sized combinations of query results, without repetition
• if K > N: empty set (no K-sized combinations exist)

pub unsafe fn iter_unchecked(
    &'s mut self,
    world: &'w World
) -> QueryIter<'w, 's, Q, <Q as WorldQuery>::Fetch, F>

Returns an Iterator over the query results for the given World.

Safety

This does not check for mutable query correctness. To be safe, make sure mutable queries have unique access to the components they query.

pub unsafe fn iter_combinations_unchecked<const K: usize>(
    &'s mut self,
    world: &'w World
) -> QueryCombinationIter<'w, 's, Q, <Q as WorldQuery>::Fetch, F, K>

Returns an Iterator over all possible combinations of K query results for the given World without repetition. This can only be called for read-only queries.

Safety

This does not check for mutable query correctness. To be safe, make sure mutable queries have unique access to the components they query.

pub fn for_each<'w, 's, FN>(&'s mut self, world: &'w World, func: FN) where
    FN: FnMut(<<Q as WorldQuery>::ReadOnlyFetch as Fetch<'w, 's>>::Item), 

Runs func on each query result for the given World. This is faster than the equivalent iter() method, but cannot be chained like a normal Iterator.

This can only be called for read-only queries, see Self::for_each_mut for write-queries.

pub fn for_each_mut<'w, 's, FN>(&'s mut self, world: &'w mut World, func: FN) where
    FN: FnMut(<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item), 

Runs func on each query result for the given World. This is faster than the equivalent iter_mut() method, but cannot be chained like a normal Iterator.

pub unsafe fn for_each_unchecked<'w, 's, FN>(
    &'s mut self,
    world: &'w World,
    func: FN
) where
    FN: FnMut(<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item), 

Runs func on each query result for the given World. This is faster than the equivalent iter() method, but cannot be chained like a normal Iterator.

This can only be called for read-only queries.

Safety

This does not check for mutable query correctness. To be safe, make sure mutable queries have unique access to the components they query.

pub fn par_for_each<'w, 's, FN>(
    &'s mut self,
    world: &'w World,
    task_pool: &TaskPool,
    batch_size: usize,
    func: FN
) where
    FN: Fn(<<Q as WorldQuery>::ReadOnlyFetch as Fetch<'w, 's>>::Item) + Send + Sync + Clone, 

Runs func on each query result in parallel using the given task_pool.

This can only be called for read-only queries, see Self::par_for_each_mut for write-queries.

pub fn par_for_each_mut<'w, 's, FN>(
    &'s mut self,
    world: &'w mut World,
    task_pool: &TaskPool,
    batch_size: usize,
    func: FN
) where
    FN: Fn(<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item) + Send + Sync + Clone, 

Runs func on each query result in parallel using the given task_pool.

pub unsafe fn par_for_each_unchecked<'w, 's, FN>(
    &'s mut self,
    world: &'w World,
    task_pool: &TaskPool,
    batch_size: usize,
    func: FN
) where
    FN: Fn(<<Q as WorldQuery>::Fetch as Fetch<'w, 's>>::Item) + Send + Sync + Clone, 

Runs func on each query result in parallel using the given task_pool.

This can only be called for read-only queries.

Safety

This does not check for mutable query correctness. To be safe, make sure mutable queries have unique access to the components they query.

Trait Implementations

impl<Q, F> FromWorld for QueryState<Q, F> where
    Q: WorldQuery,
    F: WorldQuery,
    <F as WorldQuery>::Fetch: FilterFetch, 

fn from_world(world: &mut World) -> QueryState<Q, F>

Creates Self using data from the given World

impl<'w, 's, Q, F> SystemParamFetch<'w, 's> for QueryState<Q, F> where
    Q: 'static + WorldQuery,
    F: 'static + WorldQuery,
    <F as WorldQuery>::Fetch: FilterFetch, 

type Item = Query<'w, 's, Q, F>

unsafe fn get_param(
    state: &'s mut QueryState<Q, F>,
    system_meta: &SystemMeta,
    world: &'w World,
    change_tick: u32
) -> <QueryState<Q, F> as SystemParamFetch<'w, 's>>::Item

Safety

impl<Q, F> SystemParamState for QueryState<Q, F> where
    Q: 'static + WorldQuery,
    F: 'static + WorldQuery,
    <F as WorldQuery>::Fetch: FilterFetch, 

fn init(world: &mut World, system_meta: &mut SystemMeta) -> QueryState<Q, F>

fn new_archetype(&mut self, archetype: &Archetype, system_meta: &mut SystemMeta)

fn apply(&mut self, _world: &mut World)

impl<Q, F> ReadOnlySystemParamFetch for QueryState<Q, F> where
    Q: WorldQuery,
    F: WorldQuery,
    <Q as WorldQuery>::Fetch: ReadOnlyFetch,
    <F as WorldQuery>::Fetch: FilterFetch,