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>

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes