Struct Once 

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

Single-writer, multi-reader Once cell. set may be called at most once (a second call returns Err with the value back); get returns None until then and Some(&T) forever after.

Implementations

impl<T> Once<T>

pub const fn new() -> Self

Create an empty Once.

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

Store the value (boot time, single writer). Returns Err(value) if already set.

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

Borrow the stored value, or None if not yet set.

Trait Implementations

impl<T> Default for Once<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Sync> Sync for Once<T>