Struct OnceCell 

pub struct OnceCell<T>(/* private fields */);

An Option value which can be safely written once.

Implementations

impl<T> OnceCell<T>

pub const fn empty() -> Self

Create a new, empty OnceCell.

pub const fn new(value: T) -> Self

Create a OnceCell from an owned value.

pub fn get(&self) -> Option<&T>

Get a shared reference to the contained value, if any.

pub fn get_mut(&mut self) -> Option<&mut T>

Get a mutable reference to the contained value, if any.

pub fn get_or_init(&self, init: impl FnOnce() -> T) -> &T

Get a reference to the contained value, initializing it if necessary. The initializer will only be run by one thread if multiple are in competition.

pub fn get_or_try_init<E>( &self, init: impl FnOnce() -> Result<T, E>, ) -> Result<&T, E>

Get a reference to the contained value, initializing it if necessary. The initializer will only be run by one thread if multiple are in competition.

pub fn set(&self, value: T) -> Result<(), T>

Assign the value of the OnceCell, returning Some(value) if the cell is already locked or populated.

pub fn into_inner(self) -> Option<T>

Extract the inner value.

pub fn is_locked(&self) -> bool

Check if the lock is currently acquired.

Trait Implementations

impl<T: Clone> Clone for OnceCell<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for OnceCell<T>

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

Formats the value using the given formatter.

impl<T> Default for OnceCell<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Display> Display for OnceCell<T>

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

Formats the value using the given formatter.

impl<T> From<Option<T>> for OnceCell<T>

fn from(data: Option<T>) -> Self

Converts to this type from the input type.

impl<T> From<OptionLock<T>> for OnceCell<T>

fn from(lock: OptionLock<T>) -> Self

Converts to this type from the input type.

impl<T> From<T> for OnceCell<T>

fn from(data: T) -> Self

Converts to this type from the input type.