Trait OnceExt 

pub trait OnceExt {
    type T;

    // Required methods
    fn try_borrow_with<F, E>(&self, f: F) -> Result<&Self::T, E>
       where F: FnOnce() -> Result<Self::T, E>;
    fn replace(&mut self, new_value: Self::T) -> Option<Self::T>;
    fn filled(&self) -> bool;
}

Required Associated Types

type T

Required Methods

fn try_borrow_with<F, E>(&self, f: F) -> Result<&Self::T, E>

where F: FnOnce() -> Result<Self::T, E>,

This might run f multiple times if different threads start initializing at once.

fn replace(&mut self, new_value: Self::T) -> Option<Self::T>

fn filled(&self) -> bool

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<T> OnceExt for OnceCell<T>

type T = T

fn try_borrow_with<F, E>(&self, f: F) -> Result<&T, E>

where F: FnOnce() -> Result<T, E>,

fn replace(&mut self, new_value: T) -> Option<T>

fn filled(&self) -> bool

impl<T> OnceExt for OnceLock<T>

type T = T

fn try_borrow_with<F, E>(&self, f: F) -> Result<&T, E>

where F: FnOnce() -> Result<T, E>,

fn replace(&mut self, new_value: T) -> Option<T>

fn filled(&self) -> bool

Implementors