Struct Single 

pub struct Single<'a, Q>(pub <Q as Query>::Item<'a>)
where
    Q: Query;

A HandlerParam which fetches a single entity from the world.

If there isn’t exactly one entity that matches the Query, a runtime panic occurs. This is useful for representing global variables or singleton entities.

Examples

use evenio::prelude::*;

#[derive(Component)]
struct MyComponent(i32);

let mut world = World::new();

world.add_handler(
    |_: Receiver<E>, Single(MyComponent(data)): Single<&MyComponent>| {
        println!("The data is: {data}");
    },
);

let e = world.spawn();
world.insert(e, MyComponent(123));

world.send(E);

Tuple Fields

0: <Q as Query>::Item<'a>

Trait Implementations

impl<'a, Q> Clone for Single<'a, Q>

where Q: Clone + Query, <Q as Query>::Item<'a>: Clone,

fn clone(&self) -> Single<'a, Q>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, Q> Debug for Single<'a, Q>

where Q: Debug + Query, <Q as Query>::Item<'a>: Debug,

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

Formats the value using the given formatter.

impl<'a, Q> Default for Single<'a, Q>

where Q: Default + Query, <Q as Query>::Item<'a>: Default,

fn default() -> Single<'a, Q>

Returns the “default value” for a type.

impl<'a, Q> Deref for Single<'a, Q>

where Q: Query,

type Target = <Q as Query>::Item<'a>

The resulting type after dereferencing.

fn deref(&self) -> &<Single<'a, Q> as Deref>::Target

Dereferences the value.

impl<'a, Q> DerefMut for Single<'a, Q>

where Q: Query,

fn deref_mut(&mut self) -> &mut <Single<'a, Q> as Deref>::Target

Mutably dereferences the value.

impl<Q> HandlerParam for Single<'_, Q>

where Q: Query + 'static,

type State = FetcherState<Q>

Persistent data stored in the handler.

type This<'a> = Single<'a, Q>

The type produced by this handler param. This must be the type of Self but with the lifetime of 'a.

fn init( world: &mut World, config: &mut HandlerConfig, ) -> Result<<Single<'_, Q> as HandlerParam>::State, InitError>

Initializes the handler using the input World and HandlerConfig.

unsafe fn get<'a>( state: &'a mut <Single<'_, Q> as HandlerParam>::State, info: &'a HandlerInfo, event_ptr: EventPtr<'a>, target_location: EntityLocation, world: UnsafeWorldCell<'a>, ) -> <Single<'_, Q> as HandlerParam>::This<'a>

Obtains a new instance of the handler parameter.

fn refresh_archetype( state: &mut <Single<'_, Q> as HandlerParam>::State, arch: &Archetype, )

Refresh an archetype for this handler param. Called whenever Handler::refresh_archetype is called.

fn remove_archetype( state: &mut <Single<'_, Q> as HandlerParam>::State, arch: &Archetype, )

Remove the given archetype for this handler param. Called whenever Handler::remove_archetype is called.

impl<'a, Q> Ord for Single<'a, Q>

where Q: Ord + Query, <Q as Query>::Item<'a>: Ord,

fn cmp(&self, other: &Single<'a, Q>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<'a, Q> PartialEq for Single<'a, Q>

where Q: PartialEq + Query, <Q as Query>::Item<'a>: PartialEq,

fn eq(&self, other: &Single<'a, Q>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a, Q> PartialOrd for Single<'a, Q>

where Q: PartialOrd + Query, <Q as Query>::Item<'a>: PartialOrd,

fn partial_cmp(&self, other: &Single<'a, Q>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, Q> Copy for Single<'a, Q>

where Q: Copy + Query, <Q as Query>::Item<'a>: Copy,

impl<'a, Q> Eq for Single<'a, Q>

where Q: Eq + Query, <Q as Query>::Item<'a>: Eq,

impl<'a, Q> StructuralPartialEq for Single<'a, Q>

where Q: Query,