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§
Ready(T)
Represents that a value is immediately ready.
Pending
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§
source§impl<T> Poll<Option<T>>
impl<T> Poll<Option<T>>
sourcepub fn async_gen_ready(t: T) -> Poll<Option<T>>
🔬This is a nightly-only experimental API. (async_gen_internals
)
pub fn async_gen_ready(t: T) -> Poll<Option<T>>
async_gen_internals
)A helper function for internal desugaring – produces Ready(Some(t))
,
which corresponds to the async iterator yielding a value.
source§impl<T> Poll<T>
impl<T> Poll<T>
sourcepub fn map<U, F>(self, f: F) -> Poll<U>where
F: FnOnce(T) -> U,
pub fn map<U, F>(self, f: F) -> Poll<U>where
F: FnOnce(T) -> U,
Maps a Poll<T>
to Poll<U>
by applying a function to a contained value.
§Examples
Converts a Poll<String>
into a 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));
const: 1.49.0 · sourcepub const fn is_ready(&self) -> bool
pub const fn is_ready(&self) -> bool
Returns 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);
const: 1.49.0 · sourcepub const fn is_pending(&self) -> bool
pub const fn is_pending(&self) -> bool
source§impl<T, E> Poll<Result<T, E>>
impl<T, E> Poll<Result<T, E>>
sourcepub fn map_ok<U, F>(self, f: F) -> Poll<Result<U, E>>where
F: FnOnce(T) -> U,
pub fn map_ok<U, F>(self, f: F) -> Poll<Result<U, E>>where
F: FnOnce(T) -> U,
Maps 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)));
sourcepub fn map_err<U, F>(self, f: F) -> Poll<Result<T, U>>where
F: FnOnce(E) -> U,
pub fn map_err<U, F>(self, f: F) -> Poll<Result<T, U>>where
F: FnOnce(E) -> U,
Maps 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)));
source§impl<T, E> Poll<Option<Result<T, E>>>
impl<T, E> Poll<Option<Result<T, E>>>
1.51.0 · sourcepub fn map_ok<U, F>(self, f: F) -> Poll<Option<Result<U, E>>>where
F: FnOnce(T) -> U,
pub fn map_ok<U, F>(self, f: F) -> Poll<Option<Result<U, E>>>where
F: FnOnce(T) -> U,
Maps 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))));
1.51.0 · sourcepub fn map_err<U, F>(self, f: F) -> Poll<Option<Result<T, U>>>where
F: FnOnce(E) -> U,
pub fn map_err<U, F>(self, f: F) -> Poll<Option<Result<T, U>>>where
F: FnOnce(E) -> U,
Maps 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))));
Trait Implementations§
source§impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Option<Result<T, F>>>where
F: From<E>,
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Option<Result<T, F>>>where
F: From<E>,
source§fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
try_trait_v2
)Residual
type. Read moresource§impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Result<T, F>>where
F: From<E>,
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Result<T, F>>where
F: From<E>,
source§fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
try_trait_v2
)Residual
type. Read moresource§impl<T> Ord for Poll<T>where
T: Ord,
impl<T> Ord for Poll<T>where
T: Ord,
source§impl<T> PartialEq for Poll<T>where
T: PartialEq,
impl<T> PartialEq for Poll<T>where
T: PartialEq,
source§impl<T> PartialOrd for Poll<T>where
T: PartialOrd,
impl<T> PartialOrd for Poll<T>where
T: PartialOrd,
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read more§impl<T> Sequence for Poll<T>where
T: Sequence,
impl<T> Sequence for Poll<T>where
T: Sequence,
source§impl<T, E> Try for Poll<Option<Result<T, E>>>
impl<T, E> Try for Poll<Option<Result<T, E>>>
§type Output = Poll<Option<T>>
type Output = Poll<Option<T>>
try_trait_v2
)?
when not short-circuiting.§type Residual = Result<Infallible, E>
type Residual = Result<Infallible, E>
try_trait_v2
)FromResidual::from_residual
as part of ?
when short-circuiting. Read moresource§fn from_output(
c: <Poll<Option<Result<T, E>>> as Try>::Output
) -> Poll<Option<Result<T, E>>>
fn from_output( c: <Poll<Option<Result<T, E>>> as Try>::Output ) -> Poll<Option<Result<T, E>>>
try_trait_v2
)Output
type. Read moresource§fn branch(
self
) -> ControlFlow<<Poll<Option<Result<T, E>>> as Try>::Residual, <Poll<Option<Result<T, E>>> as Try>::Output>
fn branch( self ) -> ControlFlow<<Poll<Option<Result<T, E>>> as Try>::Residual, <Poll<Option<Result<T, E>>> as Try>::Output>
try_trait_v2
)?
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 moresource§impl<T, E> Try for Poll<Result<T, E>>
impl<T, E> Try for Poll<Result<T, E>>
§type Output = Poll<T>
type Output = Poll<T>
try_trait_v2
)?
when not short-circuiting.§type Residual = Result<Infallible, E>
type Residual = Result<Infallible, E>
try_trait_v2
)FromResidual::from_residual
as part of ?
when short-circuiting. Read moresource§fn from_output(c: <Poll<Result<T, E>> as Try>::Output) -> Poll<Result<T, E>>
fn from_output(c: <Poll<Result<T, E>> as Try>::Output) -> Poll<Result<T, E>>
try_trait_v2
)Output
type. Read moresource§fn branch(
self
) -> ControlFlow<<Poll<Result<T, E>> as Try>::Residual, <Poll<Result<T, E>> as Try>::Output>
fn branch( self ) -> ControlFlow<<Poll<Result<T, E>> as Try>::Residual, <Poll<Result<T, E>> as Try>::Output>
try_trait_v2
)?
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 moreimpl<T> Copy for Poll<T>where
T: Copy,
impl<T> Eq for Poll<T>where
T: Eq,
impl<T> StructuralEq for Poll<T>
impl<T> StructuralPartialEq for Poll<T>
Auto Trait Implementations§
impl<T> RefUnwindSafe for Poll<T>where
T: RefUnwindSafe,
impl<T> Send for Poll<T>where
T: Send,
impl<T> Sync for Poll<T>where
T: Sync,
impl<T> Unpin for Poll<T>where
T: Unpin,
impl<T> UnwindSafe for Poll<T>where
T: UnwindSafe,
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
§impl<T> Conv for T
impl<T> Conv for T
§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
§impl<T> FmtForward for T
impl<T> FmtForward for T
§fn fmt_binary(self) -> FmtBinary<Self>where
Self: Binary,
fn fmt_binary(self) -> FmtBinary<Self>where
Self: Binary,
self
to use its Binary
implementation when Debug
-formatted.§fn fmt_display(self) -> FmtDisplay<Self>where
Self: Display,
fn fmt_display(self) -> FmtDisplay<Self>where
Self: Display,
self
to use its Display
implementation when
Debug
-formatted.§fn fmt_lower_exp(self) -> FmtLowerExp<Self>where
Self: LowerExp,
fn fmt_lower_exp(self) -> FmtLowerExp<Self>where
Self: LowerExp,
self
to use its LowerExp
implementation when
Debug
-formatted.§fn fmt_lower_hex(self) -> FmtLowerHex<Self>where
Self: LowerHex,
fn fmt_lower_hex(self) -> FmtLowerHex<Self>where
Self: LowerHex,
self
to use its LowerHex
implementation when
Debug
-formatted.§fn fmt_octal(self) -> FmtOctal<Self>where
Self: Octal,
fn fmt_octal(self) -> FmtOctal<Self>where
Self: Octal,
self
to use its Octal
implementation when Debug
-formatted.§fn fmt_pointer(self) -> FmtPointer<Self>where
Self: Pointer,
fn fmt_pointer(self) -> FmtPointer<Self>where
Self: Pointer,
self
to use its Pointer
implementation when
Debug
-formatted.§fn fmt_upper_exp(self) -> FmtUpperExp<Self>where
Self: UpperExp,
fn fmt_upper_exp(self) -> FmtUpperExp<Self>where
Self: UpperExp,
self
to use its UpperExp
implementation when
Debug
-formatted.§fn fmt_upper_hex(self) -> FmtUpperHex<Self>where
Self: UpperHex,
fn fmt_upper_hex(self) -> FmtUpperHex<Self>where
Self: UpperHex,
self
to use its UpperHex
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Debug
-formatted.§fn fmt_list(self) -> FmtList<Self>where
&'a Self: for<'a> IntoIterator,
fn fmt_list(self) -> FmtList<Self>where
&'a Self: for<'a> IntoIterator,
§impl<T> Pipe for Twhere
T: ?Sized,
impl<T> Pipe for Twhere
T: ?Sized,
§fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> Rwhere
Self: Sized,
fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> Rwhere
Self: Sized,
§fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> Rwhere
R: 'a,
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R: 'a,
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and passes that borrow into the pipe function. Read more§fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> Rwhere
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&'a mut self,
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) -> R
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, then passes self.as_ref()
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fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R
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§fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self
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builds.