Struct bevy::ecs::query::ChangeTrackers

pub struct ChangeTrackers<T>where
    T: Component,
{ /* private fields */ }
Expand description

WorldQuery that tracks changes and additions for component T.

Wraps a Component to track whether the component changed for the corresponding entities in a query since the last time the system that includes these queries ran.

If you only care about entities that changed or that got added use the Changed and Added filters instead.

Examples

fn print_moving_objects_system(query: Query<(&Name, ChangeTrackers<Transform>)>) {
    for (name, tracker) in &query {
        if tracker.is_changed() {
            println!("Entity moved: {:?}", name);
        } else {
            println!("Entity stood still: {:?}", name);
        }
    }
}

Implementations§

Returns true if this component has been added since the last execution of this system.

Returns true if this component has been changed since the last execution of this system.

Trait Implementations§

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Per archetype/table state used by this WorldQuery to fetch Self::Item
The item returned by this WorldQuery
The read-only variant of this WorldQuery, which satisfies the ReadOnlyWorldQuery 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. Read more
This function manually implements subtyping for the query items.
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. Read more
Returns true if (and only if) this Fetch relies strictly on archetypes to limit which components are accessed by the Query. Read more
Creates a new instance of this fetch. Read more
While this function can be called for any query, it is always safe to call if Self: ReadOnlyWorldQuery holds. Read more
Adjusts internal state to account for the next Archetype. This will always be called on archetypes that match this WorldQuery. Read more
Adjusts internal state to account for the next Table. This will always be called on tables that match this WorldQuery. Read more
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. Read more
Safety Read more

SAFETY: access is read only

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait. Read more
Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait. Read more
Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s. Read more
Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s. Read more
Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait. Read more

Returns the argument unchanged.

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
Instruments this type with the current Span, returning an Instrumented wrapper. Read more

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.
Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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