Enum core::task::Poll 1.36.0[−][src]
pub enum Poll<T> {
Ready(T),
Pending,
}Expand description
Indicates whether a value is available or if the current task has been scheduled to receive a wakeup instead.
Variants
Represents that a value is immediately ready.
Represents that a value is not ready yet.
When a function returns Pending, the function must also
ensure that the current task is scheduled to be awoken when
progress can be made.
Implementations
Maps a Poll<T> to Poll<U> by applying a function to a contained value.
Examples
Converts a Poll<String> into an Poll<usize>, consuming the original:
let poll_some_string = Poll::Ready(String::from("Hello, World!"));
// `Poll::map` takes self *by value*, consuming `poll_some_string`
let poll_some_len = poll_some_string.map(|s| s.len());
assert_eq!(poll_some_len, Poll::Ready(13));RunReturns true if the poll is a Poll::Ready value.
Examples
let x: Poll<u32> = Poll::Ready(2);
assert_eq!(x.is_ready(), true);
let x: Poll<u32> = Poll::Pending;
assert_eq!(x.is_ready(), false);RunMaps a Poll<Result<T, E>> to Poll<Result<U, E>> by applying a
function to a contained Poll::Ready(Ok) value, leaving all other
variants untouched.
This function can be used to compose the results of two functions.
Examples
let res: Poll<Result<u8, _>> = Poll::Ready("12".parse());
let squared = res.map_ok(|n| n * n);
assert_eq!(squared, Poll::Ready(Ok(144)));RunMaps a Poll::Ready<Result<T, E>> to Poll::Ready<Result<T, F>> by
applying a function to a contained Poll::Ready(Err) value, leaving all other
variants untouched.
This function can be used to pass through a successful result while handling an error.
Examples
let res: Poll<Result<u8, _>> = Poll::Ready("oops".parse());
let res = res.map_err(|_| 0_u8);
assert_eq!(res, Poll::Ready(Err(0)));RunMaps a Poll<Option<Result<T, E>>> to Poll<Option<Result<U, E>>> by
applying a function to a contained Poll::Ready(Some(Ok)) value,
leaving all other variants untouched.
This function can be used to compose the results of two functions.
Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("12".parse()));
let squared = res.map_ok(|n| n * n);
assert_eq!(squared, Poll::Ready(Some(Ok(144))));RunMaps a Poll::Ready<Option<Result<T, E>>> to
Poll::Ready<Option<Result<T, F>>> by applying a function to a
contained Poll::Ready(Some(Err)) value, leaving all other variants
untouched.
This function can be used to pass through a successful result while handling an error.
Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("oops".parse()));
let res = res.map_err(|_| 0_u8);
assert_eq!(res, Poll::Ready(Some(Err(0))));RunTrait Implementations
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <=
operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
The type of the value produced by ? when not short-circuiting.
type Residual = Result<Infallible, E>
type Residual = Result<Infallible, E>
The type of the value passed to FromResidual::from_residual
as part of ? when short-circuiting. Read more
Used in ? to decide whether the operator should produce a value
(because this returned ControlFlow::Continue)
or propagate a value back to the caller
(because this returned ControlFlow::Break). Read more
The type of the value produced by ? when not short-circuiting.
type Residual = Result<Infallible, E>
type Residual = Result<Infallible, E>
The type of the value passed to FromResidual::from_residual
as part of ? when short-circuiting. Read more
Used in ? to decide whether the operator should produce a value
(because this returned ControlFlow::Continue)
or propagate a value back to the caller
(because this returned ControlFlow::Break). Read more