pub struct LazyCell<T, F = fn() -> T> { /* private fields */ }
Expand description
A value which is initialized on the first access.
For a thread-safe version of this struct, see std::sync::LazyLock
.
§Examples
use std::cell::LazyCell;
let lazy: LazyCell<i32> = LazyCell::new(|| {
println!("initializing");
92
});
println!("ready");
println!("{}", *lazy);
println!("{}", *lazy);
// Prints:
// ready
// initializing
// 92
// 92
RunImplementations§
source§impl<T, F: FnOnce() -> T> LazyCell<T, F>
impl<T, F: FnOnce() -> T> LazyCell<T, F>
sourcepub fn into_inner(this: Self) -> Result<T, F>
🔬This is a nightly-only experimental API. (lazy_cell_into_inner
#125623)
pub fn into_inner(this: Self) -> Result<T, F>
lazy_cell_into_inner
#125623)Consumes this LazyCell
returning the stored value.
Returns Ok(value)
if Lazy
is initialized and Err(f)
otherwise.
§Examples
#![feature(lazy_cell_into_inner)]
use std::cell::LazyCell;
let hello = "Hello, World!".to_string();
let lazy = LazyCell::new(|| hello.to_uppercase());
assert_eq!(&*lazy, "HELLO, WORLD!");
assert_eq!(LazyCell::into_inner(lazy).ok(), Some("HELLO, WORLD!".to_string()));
RunTrait Implementations§
Auto Trait Implementations§
impl<T, F = fn() -> T> !Freeze for LazyCell<T, F>
impl<T, F = fn() -> T> !RefUnwindSafe for LazyCell<T, F>
impl<T, F> Send for LazyCell<T, F>
impl<T, F = fn() -> T> !Sync for LazyCell<T, F>
impl<T, F> Unpin for LazyCell<T, F>
impl<T, F> UnwindSafe for LazyCell<T, F>where
F: UnwindSafe,
T: UnwindSafe,
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more