Struct shred::MetaTable
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pub struct MetaTable<T: ?Sized> { /* fields omitted */ }
The MetaTable
which allows to store object-safe trait implementations for resources.
For example, you have a trait Foo
that is implemented by several resources.
You can register all the implementors using MetaTable::register
. Later on, you
can iterate over all resources that implement Foo
without knowing their specific type.
Examples
use shred::{CastFrom, MetaTable, Resources}; trait Object { fn method1(&self) -> i32; fn method2(&mut self, x: i32); } impl<T> CastFrom<T> for Object where T: Object + 'static, { fn cast(t: &T) -> &Self { t } fn cast_mut(t: &mut T) -> &mut Self { t } } struct ImplementorA(i32); impl Object for ImplementorA { fn method1(&self) -> i32 { self.0 } fn method2(&mut self, x: i32) { self.0 += x; } } struct ImplementorB(i32); impl Object for ImplementorB { fn method1(&self) -> i32 { self.0 } fn method2(&mut self, x: i32) { self.0 *= x; } } let mut res = Resources::new(); res.insert(ImplementorA(3)); res.insert(ImplementorB(1)); let mut table = MetaTable::<Object>::new(); table.register(&ImplementorA(31415)); // Can just be some instance of type `&ImplementorA`. table.register(&ImplementorB(27182)); { let mut iter = table.iter(&mut res); assert_eq!(iter.next().unwrap().method1(), 3); assert_eq!(iter.next().unwrap().method1(), 1); }
Methods
impl<T: ?Sized> MetaTable<T>
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pub fn new() -> Self
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Creates a new MetaTable
.
pub fn register<R>(&mut self, r: &R) where
R: Resource,
T: CastFrom<R> + 'static,
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R: Resource,
T: CastFrom<R> + 'static,
Registers a resource R
that implements the trait T
.
This just needs some instance of type R
to retrieve the vtable.
It doesn't have to be the same object you're calling get
with later.
pub fn get<'a>(&self, res: &'a Resource) -> Option<&'a T>
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Tries to convert res
to a trait object of type &T
.
If res
doesn't have an implementation for T
(or it wasn't registered),
this will return None
.
pub fn get_mut<'a>(&self, res: &'a Resource) -> Option<&'a mut T>
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Tries to convert res
to a trait object of type &mut T
.
If res
doesn't have an implementation for T
(or it wasn't registered),
this will return None
.
ⓘImportant traits for MetaIter<'a, T>pub fn iter<'a>(&'a self, res: &'a Resources) -> MetaIter<'a, T>
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Iterates all resources that implement T
and were registered.
ⓘImportant traits for MetaIterMut<'a, T>pub fn iter_mut<'a>(&'a self, res: &'a Resources) -> MetaIterMut<'a, T>
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Iterates all resources that implement T
and were registered mutably.