[英]Rust: type reference within trait
I would like to implement my own generic container, and this is the fragment of a trait I am using:我想实现自己的通用容器,这是我正在使用的特征的片段:
pub trait MyVec
where
Self: Default + Clone + IntoIterator,
Self: std::iter::FromIterator<<Self as IntoIterator>::Item>,
{
fn get(self: &Self, index: usize) -> <Self as IntoIterator>::Item;
// many other methods are omitted.
}
Is it possible to introduce a new computed type variable so that I can avoid typing <Self as IntoIterator>::Item
everywhere?是否可以引入一个新的计算类型变量,这样我就可以避免在任何地方输入
<Self as IntoIterator>::Item
? A simple type Item = <Self as IntoIterator>::Item
does not work because that is an associated type that could potentially be overridden.一个简单的
type Item = <Self as IntoIterator>::Item
不起作用,因为这是一个可能被覆盖的关联类型。 Using a type parameter as MyVec<I>
does not work either as I do not want to implement this trait with different I
types for the same struct, and it also causes problem when writing generic code later.使用类型参数作为
MyVec<I>
也不起作用,因为我不想用不同的I
类型为同一个结构实现这个特性,并且在以后编写通用代码时也会导致问题。 Any recommendations?有什么建议吗?
I don't think you can define a type
in the trait
as implementors then could customize this type.我不认为你可以在
trait
中定义一个type
作为实现者然后可以自定义这个类型。
But you could introduce a type alias outside the trait:但是你可以在特征之外引入一个类型别名:
pub type IntoIterItem<T> = <T as IntoIterator>::Item;
pub trait MyVec :
Default
+ Clone
+ IntoIterator
+ std::iter::FromIterator<IntoIterItem<Self>>
{
fn get(self: &Self, index: usize) -> IntoIterItem<Self>;
}
Or, as a hack, you could try MyVec<I>
, but with a default I
:或者,作为 hack,您可以尝试
MyVec<I>
,但使用默认值I
:
pub trait MyVec<Item=<Self as IntoIterator>::Item> :
Default
+ Clone
+ IntoIterator
+ std::iter::FromIterator<Item>
{
fn get(self: &Self, index: usize) -> Item;
}
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