Struct OnceBox

pub struct OnceBox<T> { /* private fields */ }

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

Implementations

impl<T> OnceBox<T>

pub const fn new() -> OnceBox<T>

Creates a new empty cell.

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

Gets a reference to the underlying value.

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

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) -> &T

where F: FnOnce() -> Box<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<&T, E>

where F: FnOnce() -> Result<Box<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<T> Debug for OnceBox<T>

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

Formats the value using the given formatter.

impl<T> Default for OnceBox<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> Drop for OnceBox<T>

fn drop(&mut self)

Executes the destructor for this type.

impl<T: Sync + Send> Sync for OnceBox<T>