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use std::any::{type_name, Any};
use std::fmt::Debug;
use std::ops::{Deref, DerefMut};
use crate::uid::Uid;
use crate::component::HandleMut as ComponentHandleMut;
use crate::component::IntoParts as IntoComponentParts;
use crate::system::{Metadata as SystemMetadata, Param as SystemParam};
use crate::World;
/// A type which has a single instance and is shared globally.
pub trait Sole: Any + IntoComponentParts
{
fn id() -> Uid
where
Self: Sized;
fn type_reflection() -> Option<&'static crate::reflection::Type>
where
Self: Sized;
/// Returns the name of this component.
fn name(&self) -> &'static str;
}
impl dyn Sole
{
pub fn downcast_mut<Real: 'static>(&mut self) -> Option<&mut Real>
{
(self as &mut dyn Any).downcast_mut()
}
pub fn downcast_ref<Real: 'static>(&self) -> Option<&Real>
{
(self as &dyn Any).downcast_ref()
}
pub fn is<Other: 'static>(&self) -> bool
{
(self as &dyn Any).is::<Other>()
}
}
impl Debug for dyn Sole
{
fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
{
formatter.debug_struct("Sole").finish_non_exhaustive()
}
}
/// Holds a reference to a globally shared singleton value.
#[derive(Debug)]
pub struct Single<'world, SoleT: Sole>
{
sole: ComponentHandleMut<'world, SoleT>,
}
impl<'world, SoleT> Single<'world, SoleT>
where
SoleT: Sole,
{
pub(crate) fn new(sole: ComponentHandleMut<'world, SoleT>) -> Self
{
Self { sole }
}
}
impl<'world, SoleT> SystemParam<'world> for Single<'world, SoleT>
where
SoleT: Sole,
{
type Input = ();
fn new(world: &'world World, _system_metadata: &SystemMetadata) -> Self
{
let sole = world
.get_entity(SoleT::id())
.and_then(|ent| ent.get_with_id_mut::<SoleT>(SoleT::id()))
.unwrap_or_else(|| {
panic!("Sole component {} was not found in world", type_name::<SoleT>())
});
Self::new(sole)
}
}
impl<SoleT> Deref for Single<'_, SoleT>
where
SoleT: Sole,
{
type Target = SoleT;
fn deref(&self) -> &Self::Target
{
&*self.sole
}
}
impl<SoleT> DerefMut for Single<'_, SoleT>
where
SoleT: Sole,
{
fn deref_mut(&mut self) -> &mut Self::Target
{
&mut *self.sole
}
}
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