Struct QueryBorrow 

pub struct QueryBorrow<'w, Q: Query, F: ArchetypeFilter = ()> {
    world: &'w World,
    scope: Entity,
    filter: F,
    claims: Claims<'w>,
    asks: Vec<(TypeId, &'static str, Mode)>,
    origin: &'static Location<'static>,
    marker: PhantomData<fn() -> Q>,
}

What a scope hands out for a query: the claims, and the way to iterate them.

The holder is created by crate::Scope::query and claims the components the query reaches, archetype by archetype, before it hands out anything. Iterating is QueryBorrow::iter, and every item it yields borrows from this holder, so the claims outlive the items by construction.

Dropping the holder releases the claims. Forgetting it instead (core::mem::forget) leaks them: the components stay claimed for the rest of the world’s life, and the next query for them panics rather than running alongside.

Fields

world: &'w World

scope: Entity

filter: F

claims: Claims<'w>

asks: Vec<(TypeId, &'static str, Mode)>

The buffer a pass over the archetypes records its asks in, kept here so that a second pass reuses it rather than allocating again.

origin: &'static Location<'static>

marker: PhantomData<fn() -> Q>

Implementations

impl<'w, Q: Query> QueryBorrow<'w, Q, ()>

pub(crate) fn new( world: &'w World, scope: Entity, origin: &'static Location<'static>, ) -> Self

impl<'w, Q: Query, F: ArchetypeFilter> QueryBorrow<'w, Q, F>

pub fn by<G: ArchetypeFilter>(self, filter: G) -> QueryBorrow<'w, Q, G>

Visit only the archetypes the filter accepts.

The filter sees an archetype before any of its rows is fetched and before any value is reached, so rejecting an archetype costs one test rather than one per row, and works even when that archetype’s components are already claimed elsewhere. See ArchetypeFilter.

It may be applied part-way through an iteration, and then narrows the archetype being visited too: what the filter rejects is not fetched, and the rows already yielded stay yielded.

pub fn iter(&mut self) -> QueryIter<'_, 'w, Q>

Iterate the visible entities that match Q.

The items borrow from this holder, so they cannot outlive it and it cannot be iterated for one item at a time while another is alive: collect them, or finish with each row before reaching for the next.

Trait Implementations

impl<Q: Query, F: ArchetypeFilter> Debug for QueryBorrow<'_, Q, F>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.