Module aws_smithy_async::future::now_or_later
source · Expand description
Provides the NowOrLater
future with an explicit Now
variant
When a future is immediately, ready, this enables avoiding an unnecessary allocation.
This is intended to be used with Pin<Box<dyn Future>>
or similar as the future variant. For
convenience, BoxFuture
is provided for this use case.
Typically, this is used when creating a manual async trait. In this case, it’s critical that the lifetime is captured to enable interop with the async-trait macro.
§Examples
mod future {
use aws_smithy_async::future::now_or_later::{NowOrLater, BoxFuture};
use std::future::Future;
pub struct ProvideRegion<'a>(NowOrLater<Option<String>, BoxFuture<'a, Option<String>>>);
impl<'a> ProvideRegion<'a> {
pub fn new(f: impl Future<Output = Option<String>> + Send + 'a) -> Self {
Self(NowOrLater::new(Box::pin(f)))
}
pub fn ready(region: Option<String>) -> Self {
Self(NowOrLater::ready(region))
}
}
}
pub trait ProvideRegion {
fn provide_region<'a>(&'a self) -> future::ProvideRegion<'a> where Self: 'a;
}
struct AsyncRegionProvider;
impl AsyncRegionProvider {
async fn region(&self) -> Option<String> {
todo!()
}
}
impl ProvideRegion for AsyncRegionProvider {
fn provide_region<'a>(&'a self) -> future::ProvideRegion<'a> where Self: 'a {
future::ProvideRegion::new(self.region())
}
}
Structs§
- Future with an explicit
Now
variant
Enums§
- Zero sized type for using NowOrLater when no future variant exists.
Type Aliases§
- Boxed future type alias