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use std::any::Any;
use std::ops::{Deref, DerefMut};
use crate::component::{Component, Id};
use crate::system::{ComponentRefMut, Param as SystemParam, System};
use crate::World;
/// Holds a component which is local to a single system.
#[derive(Debug)]
pub struct Local<'world, LocalComponent: Component>
{
local_component: ComponentRefMut<'world, LocalComponent>,
}
unsafe impl<'world, LocalComponent> SystemParam<'world> for Local<'world, LocalComponent>
where
LocalComponent: Component,
{
type Flags = ();
type Input = LocalComponent;
fn initialize<SystemImpl>(
system: &mut impl System<'world, SystemImpl>,
input: Self::Input,
)
{
system.set_local_component(input);
}
fn new<SystemImpl>(
system: &'world impl System<'world, SystemImpl>,
_world: &'world World,
) -> Self
{
let local_component = system
.get_local_component_mut::<LocalComponent>()
.expect("Local component is uninitialized");
Self { local_component }
}
fn is_compatible<Other: SystemParam<'world>>() -> bool
{
let other_comparable = Other::get_comparable();
let Some(other_id) = other_comparable.downcast_ref::<Id>() else {
return true;
};
Id::of::<LocalComponent>() != *other_id
}
fn get_comparable() -> Box<dyn Any>
{
Box::new(Id::of::<LocalComponent>())
}
}
impl<'world, LocalComponent> Deref for Local<'world, LocalComponent>
where
LocalComponent: Component,
{
type Target = LocalComponent;
fn deref(&self) -> &Self::Target
{
&self.local_component
}
}
impl<'world, LocalComponent> DerefMut for Local<'world, LocalComponent>
where
LocalComponent: Component,
{
fn deref_mut(&mut self) -> &mut Self::Target
{
&mut self.local_component
}
}
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