Struct One

pub struct One<T>(pub T);

WorldQuery adapter that fetches entities with exactly one component implementing a trait.

Depending on whether you requested shared or exclusive access to the trait objects, iterating over these queries yields types with different capacities

• Query<One<&dyn Trait>> yields a Ref object
• Query<One<&mut dyn Trait>> yields a Mut object

Tuple Fields

0: T

Trait Implementations

impl<Trait: ?Sized + TraitQuery> QueryData for One<&Trait>

const IS_READ_ONLY: bool = true

True if this query is read-only and may not perform mutable access.

type ReadOnly = One<&Trait>

The read-only variant of this QueryData, which satisfies the ReadOnlyQueryData trait.

type Item<'w> = Ref<'w, Trait>

The item returned by this WorldQuery This will be the data retrieved by the query, and is visible to the end user when calling e.g. Query<Self>::get.

fn shrink<'wlong: 'wshort, 'wshort>( item: QueryItem<'wlong, Self>, ) -> QueryItem<'wshort, Self>

This function manually implements subtyping for the query items.

unsafe fn fetch<'w>( fetch: &mut Self::Fetch<'w>, entity: Entity, table_row: TableRow, ) -> Self::Item<'w>

Fetch Self::Item for either the given entity in the current Table, or for the given entity in the current Archetype. This must always be called after WorldQuery::set_table with a table_row in the range of the current Table or after WorldQuery::set_archetype with an entity in the current archetype. Accesses components registered in WorldQuery::update_component_access.

impl<'a, Trait: ?Sized + TraitQuery> QueryData for One<&'a mut Trait>

const IS_READ_ONLY: bool = false

True if this query is read-only and may not perform mutable access.

type ReadOnly = One<&'a Trait>

The read-only variant of this QueryData, which satisfies the ReadOnlyQueryData trait.

type Item<'w> = Mut<'w, Trait>

The item returned by this WorldQuery This will be the data retrieved by the query, and is visible to the end user when calling e.g. Query<Self>::get.

fn shrink<'wlong: 'wshort, 'wshort>( item: QueryItem<'wlong, Self>, ) -> QueryItem<'wshort, Self>

This function manually implements subtyping for the query items.

unsafe fn fetch<'w>( fetch: &mut Self::Fetch<'w>, entity: Entity, table_row: TableRow, ) -> Mut<'w, Trait>

Fetch Self::Item for either the given entity in the current Table, or for the given entity in the current Archetype. This must always be called after WorldQuery::set_table with a table_row in the range of the current Table or after WorldQuery::set_archetype with an entity in the current archetype. Accesses components registered in WorldQuery::update_component_access.

impl<Trait: ?Sized + TraitQuery> WorldQuery for One<&Trait>

const IS_DENSE: bool = false

Returns true if (and only if) every table of every archetype matched by this fetch contains all of the matched components.

type Fetch<'w> = OneTraitFetch<'w, Trait>

Per archetype/table state retrieved by this WorldQuery to compute Self::Item for each entity.

type State = TraitQueryState<Trait>

State used to construct a Self::Fetch. This will be cached inside QueryState, so it is best to move as much data / computation here as possible to reduce the cost of constructing Self::Fetch.

unsafe fn init_fetch<'w>( world: UnsafeWorldCell<'w>, _state: &Self::State, _last_run: Tick, _this_run: Tick, ) -> OneTraitFetch<'w, Trait>

Creates a new instance of Self::Fetch, by combining data from the World with the cached Self::State. Readonly accesses resources registered in WorldQuery::update_component_access.

unsafe fn set_archetype<'w>( fetch: &mut OneTraitFetch<'w, Trait>, state: &Self::State, _archetype: &'w Archetype, table: &'w Table, )

Adjusts internal state to account for the next Archetype. This will always be called on archetypes that match this WorldQuery.

unsafe fn set_table<'w>( fetch: &mut OneTraitFetch<'w, Trait>, state: &Self::State, table: &'w Table, )

Adjusts internal state to account for the next Table. This will always be called on tables that match this WorldQuery.

fn update_component_access( state: &Self::State, access: &mut FilteredAccess<ComponentId>, )

Adds any component accesses used by this WorldQuery to access.

fn init_state(world: &mut World) -> Self::State

Creates and initializes a State for this WorldQuery type.

fn get_state(_: &Components) -> Option<Self::State>

Attempts to initialize a State for this WorldQuery type using read-only access to Components.

fn matches_component_set( state: &Self::State, set_contains_id: &impl Fn(ComponentId) -> bool, ) -> bool

Returns true if this query matches a set of components. Otherwise, returns false.

fn shrink_fetch<'wlong: 'wshort, 'wshort>( fetch: Self::Fetch<'wlong>, ) -> Self::Fetch<'wshort>

This function manually implements subtyping for the query fetches.

fn set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)

Sets available accesses for implementors with dynamic access such as FilteredEntityRef or FilteredEntityMut.

impl<Trait: ?Sized + TraitQuery> WorldQuery for One<&mut Trait>

const IS_DENSE: bool = false

Returns true if (and only if) every table of every archetype matched by this fetch contains all of the matched components.

type Fetch<'w> = OneTraitFetch<'w, Trait>

Per archetype/table state retrieved by this WorldQuery to compute Self::Item for each entity.

type State = TraitQueryState<Trait>

State used to construct a Self::Fetch. This will be cached inside QueryState, so it is best to move as much data / computation here as possible to reduce the cost of constructing Self::Fetch.

unsafe fn init_fetch<'w>( world: UnsafeWorldCell<'w>, _state: &Self::State, last_run: Tick, this_run: Tick, ) -> OneTraitFetch<'w, Trait>

Creates a new instance of Self::Fetch, by combining data from the World with the cached Self::State. Readonly accesses resources registered in WorldQuery::update_component_access.

unsafe fn set_archetype<'w>( fetch: &mut OneTraitFetch<'w, Trait>, state: &Self::State, _archetype: &'w Archetype, table: &'w Table, )

Adjusts internal state to account for the next Archetype. This will always be called on archetypes that match this WorldQuery.

unsafe fn set_table<'w>( fetch: &mut OneTraitFetch<'w, Trait>, state: &Self::State, table: &'w Table, )

Adjusts internal state to account for the next Table. This will always be called on tables that match this WorldQuery.

fn update_component_access( state: &Self::State, access: &mut FilteredAccess<ComponentId>, )

Adds any component accesses used by this WorldQuery to access.

fn init_state(world: &mut World) -> Self::State

Creates and initializes a State for this WorldQuery type.

fn get_state(_: &Components) -> Option<Self::State>

Attempts to initialize a State for this WorldQuery type using read-only access to Components.

fn matches_component_set( state: &Self::State, set_contains_id: &impl Fn(ComponentId) -> bool, ) -> bool

Returns true if this query matches a set of components. Otherwise, returns false.

fn shrink_fetch<'wlong: 'wshort, 'wshort>( fetch: Self::Fetch<'wlong>, ) -> Self::Fetch<'wshort>

This function manually implements subtyping for the query fetches.

fn set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)

Sets available accesses for implementors with dynamic access such as FilteredEntityRef or FilteredEntityMut.

impl<Trait: ?Sized + TraitQuery> ReadOnlyQueryData for One<&Trait>