pub enum Fetch<T> {
Ready(T),
Pending(BoxFuture<'static, T>),
}
Expand description
An in-progress request to fetch some data.
A Fetch
represents the period of uncertainty after some data has been requested, before it
is known whether that data exists locally or must be retrieved from an external source (or
whether we must wait for the data to be created in the first place).
For data that is already available locally, a request for that data may return Fetch::Ready
with the data itself. Otherwise, the request will return Fetch::Pending
with a future that
will resolve once the data is available.
Depending on the context, Fetch
can behave a bit like a Future
or a bit
like a Result
. Therefore, it implements IntoFuture
, so it can be awaited (this is the
same as calling resolve
) and it implements methods context
and with_context
, which make it easy to convert a Fetch
to a
Result
, mimicking the methods from Snafu traits OptionExt
and
ResultExt
.
Variants§
Implementations§
Source§impl<T> Fetch<T>
impl<T> Fetch<T>
Sourcepub fn try_resolve(self) -> Result<T, Self>
pub fn try_resolve(self) -> Result<T, Self>
Get the requested data if it is available immediately.
If the requested data is not immediately available, Err(self)
is returned so that the
Fetch
object may be used again.
Sourcepub fn context<C, E>(self, context: C) -> Result<T, E>where
C: IntoError<E, Source = NoneError>,
E: Error + ErrorCompat,
pub fn context<C, E>(self, context: C) -> Result<T, E>where
C: IntoError<E, Source = NoneError>,
E: Error + ErrorCompat,
Sourcepub fn with_context<F, C, E>(self, context: F) -> Result<T, E>
pub fn with_context<F, C, E>(self, context: F) -> Result<T, E>
Sourcepub fn is_pending(&self) -> bool
pub fn is_pending(&self) -> bool
Does this fetch represent an unresolved query?
Source§impl<T: Send + 'static> Fetch<T>
impl<T: Send + 'static> Fetch<T>
Sourcepub async fn with_timeout(self, timeout_duration: Duration) -> Option<T>
pub async fn with_timeout(self, timeout_duration: Duration) -> Option<T>
Wait for the requested data to become available, but only for up to timeout
.
This function is similar to resolve
, but if the future does not resolve
within timeout
, then with_timeout
will resolve with None
.
Trait Implementations§
Source§impl<T: Send + 'static> IntoFuture for Fetch<T>
impl<T: Send + 'static> IntoFuture for Fetch<T>
Source§type IntoFuture = Pin<Box<dyn Future<Output = <Fetch<T> as IntoFuture>::Output> + Send>>
type IntoFuture = Pin<Box<dyn Future<Output = <Fetch<T> as IntoFuture>::Output> + Send>>
Source§fn into_future(self) -> Self::IntoFuture
fn into_future(self) -> Self::IntoFuture
Auto Trait Implementations§
impl<T> Freeze for Fetch<T>where
T: Freeze,
impl<T> !RefUnwindSafe for Fetch<T>
impl<T> Send for Fetch<T>where
T: Send,
impl<T> !Sync for Fetch<T>
impl<T> Unpin for Fetch<T>where
T: Unpin,
impl<T> !UnwindSafe for Fetch<T>
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