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//! Component events.
use std::convert::Infallible;
use crate::component::{Handle as ComponentHandle, HandleMut as ComponentHandleMut};
use crate::entity::Handle as EntityHandle;
use crate::pair::Pair;
use crate::system::observer::EventMatch;
use crate::util::impl_multiple;
use crate::Component;
/// Pair relation for events emitted when:
/// a) A entity with the target component is spawned.
/// b) The target component is added to a entity.
#[derive(Debug, Component)]
pub struct Added(Infallible);
/// Pair relation for events emitted **before**:
/// a) The target component is removed from a entity.
/// b) A entity with the target component is despawned.
#[derive(Debug, Component)]
pub struct Removed(Infallible);
#[derive(Debug, Component)]
pub struct Changed(Infallible);
impl_multiple!(
EventMatch,
(
impl<Target: Component> _<'_><Pair<Removed, Target>> (removed),
impl<Target: Component> _<'_><Pair<Added, Target>> (added),
impl<Target: Component> _<'_><Pair<Changed, Target>> (changed)
)
cb=(type_params=(observable_type), event_name) => {
paste::paste! {
#[must_use]
pub fn [<get_ $event_name _comp>](&self) -> ComponentHandle<'_, Target>
{
let ent = self.get_ent_infallible();
let Some(comp) = ent.get::<Target>() else {
unreachable!();
};
comp
}
#[must_use]
pub fn [<get_ $event_name _comp_mut>](&self) -> ComponentHandleMut<'_, Target>
{
let ent = self.get_ent_infallible();
let Some(comp) = ent.get_mut::<Target>() else {
unreachable!();
};
comp
}
}
#[must_use]
pub fn get_ent_infallible(&self) -> EntityHandle<'_>
{
let Some(ent) = self.get_entity() else {
unreachable!();
};
ent
}
}
);
|
