Struct With

pub struct With<T>(/* private fields */);

Filter that selects entities with a component T.

This can be used in a Query if entities are required to have the component T but you don’t actually care about components value.

This is the negation of Without.

Examples

fn compliment_entity_system(query: Query<&Name, With<IsBeautiful>>) {
    for name in &query {
        println!("{} is looking lovely today!", name.name);
    }
}

Trait Implementations

impl<T: Component> QueryFilter for With<T>

const IS_ARCHETYPAL: bool = true

Returns true if (and only if) this Filter relies strictly on archetypes to limit which components are accessed by the Query.

unsafe fn filter_fetch( _fetch: &mut Self::Fetch<'_>, _entity: Entity, _table_row: TableRow, ) -> bool

Returns true if the provided Entity and TableRow should be included in the query results. If false, the entity will be skipped.

impl<T: Component> WorldQuery for With<T>

SAFETY: update_component_access does not add any accesses. This is sound because fetch does not access any components. update_component_access adds a With filter for T. This is sound because matches_component_set returns whether the set contains the component.

const IS_DENSE: bool = _

Returns true if (and only if) every table of every archetype matched by this fetch contains all of the matched components. This is used to select a more efficient “table iterator” for “dense” queries. If this returns true, WorldQuery::set_table must be used before WorldQuery::fetch can be called for iterators. If this returns false, WorldQuery::set_archetype must be used before WorldQuery::fetch can be called for iterators.

type Item<'w> = ()

The item returned by this WorldQuery For QueryData this will be the item returned by the query. For QueryFilter this will be either (), or a bool indicating whether the entity should be included or a tuple of such things.

type Fetch<'w> = ()

Per archetype/table state used by this WorldQuery to fetch Self::Item

type State = ComponentId

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.

fn shrink<'wlong: 'wshort, 'wshort>( _: Self::Item<'wlong>, ) -> Self::Item<'wshort>

This function manually implements subtyping for the query items.

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

This function manually implements subtyping for the query fetches.

unsafe fn init_fetch( _world: UnsafeWorldCell<'_>, _state: &ComponentId, _last_run: Tick, _this_run: Tick, )

Creates a new instance of this fetch.

unsafe fn set_archetype( _fetch: &mut (), _state: &ComponentId, _archetype: &Archetype, _table: &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(_fetch: &mut (), _state: &ComponentId, _table: &Table)

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

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 a entity in the current archetype.

fn update_component_access( id: &ComponentId, access: &mut FilteredAccess<ComponentId>, )

Adds any component accesses used by this WorldQuery to access.

fn init_state(world: &mut World) -> ComponentId

Creates and initializes a State for this WorldQuery type.

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

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

fn matches_component_set( id: &ComponentId, set_contains_id: &impl Fn(ComponentId) -> bool, ) -> bool

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

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

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

impl<T: Component> ArchetypeFilter for With<T>