Struct bevy::ecs::query::Added

pub struct Added<T>(_);

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,

type Fetch = AddedFetch<'w, T>

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

type Item = 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.

const IS_DENSE: bool = { match <T::Storage>::STORAGE_TYPE { StorageType::Table => true, StorageType::SparseSet => false, } }

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.

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