pub struct OnceRef<'a, T> { /* private fields */ }
Expand description

A thread-safe cell which can be written to only once.

Implementations§

§

impl<'a, T> OnceRef<'a, T>

pub const fn new() -> OnceRef<'a, T>

Creates a new empty cell.

pub fn get(&self) -> Option<&'a T>

Gets a reference to the underlying value.

pub fn set(&self, value: &'a T) -> Result<(), ()>

Sets the contents of this cell to value.

Returns Ok(()) if the cell was empty and Err(value) if it was full.

pub fn get_or_init<F>(&self, f: F) -> &'a Twhere F: FnOnce() -> &'a T,

Gets the contents of the cell, initializing it with f if the cell was empty.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&'a T, E>where F: FnOnce() -> Result<&'a T, E>,

Gets the contents of the cell, initializing it with f if the cell was empty. If the cell was empty and f failed, an error is returned.

If several threads concurrently run get_or_init, more than one f can be called. However, all threads will return the same value, produced by some f.

Trait Implementations§

§

impl<'a, T> Debug for OnceRef<'a, T>

§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
§

impl<'a, T> Default for OnceRef<'a, T>

§

fn default() -> OnceRef<'a, T>

Returns the “default value” for a type. Read more
§

impl<'a, T> Sync for OnceRef<'a, T>where T: Sync,

Auto Trait Implementations§

§

impl<'a, T> !RefUnwindSafe for OnceRef<'a, T>

§

impl<'a, T> Send for OnceRef<'a, T>where T: Sync,

§

impl<'a, T> Unpin for OnceRef<'a, T>

§

impl<'a, T> UnwindSafe for OnceRef<'a, T>where T: RefUnwindSafe,

Blanket Implementations§

source§

impl<T> Any for Twhere T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> From<T> for T

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T> Instrument for T

source§

fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
source§

fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
source§

impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T> Same<T> for T

§

type Output = T

Should always be Self
source§

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
§

impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

§

fn vzip(self) -> V

source§

impl<T> WithSubscriber for T

source§

fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
source§

fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more