Struct OnceLock 

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

A cell that can be written exactly once and is safe to share across threads.

Equivalent to std::sync::OnceLock. The first call to get_or_init runs the initializer; all subsequent calls block until initialization completes and then return a reference to the stored value.

Implementations

impl<T> OnceLock<T>

pub const fn new() -> Self

Creates a new uninitialized OnceLock.

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

Returns a reference to the value if initialized, otherwise None.

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

Returns a mutable reference to the value if initialized, otherwise None.

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

Returns the value, initializing it with f if this is the first call.

If another thread is already initializing the value, this call blocks until initialization completes.

Trait Implementations

impl<T> Drop for OnceLock<T>

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl<T: Send> Send for OnceLock<T>

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