Struct Added 

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

A filter on a component that only retains results added after the system last ran.

A common use for this filter is one-time initialization.

To retain all results without filtering but still check whether they were added after the system last ran, use ChangeTrackers<T>.

Examples

fn print_add_name_component(query: Query<&Name, Added<Name>>) {
    for name in &query {
        println!("Named entity created: {:?}", name)
    }
}

Trait Implementations

impl<T> WorldQuery for Added<T>

where T: 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.

const IS_ARCHETYPAL: bool = false

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

type Fetch<'w> = AddedFetch<'w, T>

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

type Item<'w> = bool

The item returned by this WorldQuery

type ReadOnly = Added<T>

The read-only variant of this WorldQuery, which satisfies the ReadOnlyWorldQuery trait.

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>( item: <Added<T> as WorldQuery>::Item<'wlong>, ) -> <Added<T> as WorldQuery>::Item<'wshort>

where 'wlong: 'wshort,

This function manually implements subtyping for the query items.

unsafe fn init_fetch<'w>( world: &'w World, _: &ComponentId, last_change_tick: u32, change_tick: u32, ) -> <Added<T> as WorldQuery>::Fetch<'w>

Creates a new instance of this fetch.

unsafe fn clone_fetch<'w>( fetch: &<Added<T> as WorldQuery>::Fetch<'w>, ) -> <Added<T> as WorldQuery>::Fetch<'w>

While this function can be called for any query, it is always safe to call if Self: ReadOnlyWorldQuery holds.

unsafe fn set_table<'w>( fetch: &mut <Added<T> as WorldQuery>::Fetch<'w>, _: &ComponentId, table: &'w Table, )

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

unsafe fn set_archetype<'w>( fetch: &mut <Added<T> as WorldQuery>::Fetch<'w>, component_id: &ComponentId, _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 fetch<'w>( fetch: &mut <Added<T> as WorldQuery>::Fetch<'w>, entity: Entity, table_row: usize, ) -> <Added<T> as WorldQuery>::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.

unsafe fn filter_fetch<'w>( fetch: &mut <Added<T> as WorldQuery>::Fetch<'w>, entity: Entity, table_row: usize, ) -> bool

Safety

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

fn update_archetype_component_access( _: &ComponentId, archetype: &Archetype, access: &mut Access<ArchetypeComponentId>, )

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

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

impl<T> ReadOnlyWorldQuery for Added<T>

where T: Component,

SAFETY: read-only access