Struct OnceLock 

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

A cell that can be written to only once (Rust 2024 compatible)

Similar to std::sync::OnceLock but works in no_std environments.

Implementations

impl<T> OnceLock<T>

pub const fn new() -> Self

Create a new empty OnceLock

pub fn get(&self) -> Option<&'static T>

Get the value if initialized

pub unsafe fn get_mut(&self) -> Option<&'static mut T>

Get mutable reference if initialized (unsafe)

Safety

Caller must ensure exclusive access to the contained value for the duration of the returned reference’s lifetime. No other references (mutable or immutable) to the inner value may exist concurrently. Violating this invariant causes undefined behavior due to aliased mutable references.

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

Initialize the cell with a value

Returns Ok(()) if initialization succeeds, Err(value) if already initialized

pub fn get_or_init<F>(&self, f: F) -> &'static T

where F: FnOnce() -> T,

Get or initialize the value

Trait Implementations

impl<T> Default for OnceLock<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> Drop for OnceLock<T>

fn drop(&mut self)

Executes the destructor for this type.

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

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