Trait substrate::type_dispatch::DispatchConst
source · pub trait DispatchConst {
type Constant;
const CONST: Self::Constant;
}
Expand description
A dispatch of a constant.
Prefer using the dispatch_const
macro unless the dispatcher will
be used several times.
§Examples
#[derive(Debug, Default, PartialEq, Eq)]
struct Painting(Vec<usize>);
impl Painting {
fn draw(&mut self, stroke: usize) {
self.0.push(2 * stroke)
}
}
#[derive(Debug, Default, PartialEq, Eq)]
struct Photoshop(Vec<usize>);
impl Photoshop {
fn draw(&mut self, filter: usize) {
self.0.push(5 * filter)
}
}
#[derive(Default)]
struct Dispatcher<T>(PhantomData<T>);
impl DispatchConst for Dispatcher<Painting> {
type Constant = usize;
const CONST: Self::Constant = 5;
}
impl DispatchConst for Dispatcher<Photoshop> {
type Constant = usize;
const CONST: Self::Constant = 3;
}
struct SingleStrokeMasterpiece;
#[impl_dispatch({Painting; Photoshop})]
impl<A> Into<A> for SingleStrokeMasterpiece {
fn into(self) -> A {
let mut drawing = A::default();
drawing.draw(Dispatcher::<A>::CONST);
drawing
}
}
let painting: Painting = SingleStrokeMasterpiece.into();
let photoshop: Photoshop = SingleStrokeMasterpiece.into();
assert_eq!(painting, Painting(vec![10]));
assert_eq!(photoshop, Photoshop(vec![15]));
Required Associated Types§
Required Associated Constants§
Object Safety§
This trait is not object safe.