Struct OnceCell 

pub struct OnceCell<T> {
    value: UnsafeCell<MaybeUninit<T>>,
    init: Ready,
}

A synchronization primitive that represents a value that is initialized at most once.

Fields

value: UnsafeCell<MaybeUninit<T>>

init: Ready

Implementations

impl<T> OnceCell<T>

pub const fn new() -> Self

Initializes a new OnceCell.

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

Returns a reference to the value if it is initialized.

pub fn set_or_get(&self, value: T) -> &T

Sets the value if it is not already initialized, and returns a reference to the value.

pub fn do_or_get<F>(&self, f: F) -> &T

where F: FnOnce() -> T,

Sets the value if it is not already initialized, and returns a reference to the value.

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

Sets the value if it is not already initialized, returns a reference to the value if it was not set previously.

unsafe fn get_unchecked(&self) -> &T

Returns a reference to the value, unchecked.

Safety

Preconditions: The value must be initialized. Postconditions: The value is returned.

Trait Implementations

impl<T> Sync for OnceCell<T>

Safety:

1. A value is only written to atomically and once.
2. A value is only readable from after the initialization process is finished.
3. A init is only written and read from atomically.