pub struct LazyCell<T, F = fn() -> T> { /* private fields */ }
🔬This is a nightly-only experimental API. (
lazy_cell
)Expand description
A value which is initialized on the first access.
For a thread-safe version of this struct, see std::sync::LazyLock
.
Examples
#![feature(lazy_cell)]
use std::cell::LazyCell;
let lazy: LazyCell<i32> = LazyCell::new(|| {
println!("initializing");
92
});
println!("ready");
println!("{}", *lazy);
println!("{}", *lazy);
// Prints:
// ready
// initializing
// 92
// 92
Implementations§
source§impl<T, F> LazyCell<T, F>where
F: FnOnce() -> T,
impl<T, F> LazyCell<T, F>where F: FnOnce() -> T,
sourcepub const fn new(f: F) -> LazyCell<T, F>
🔬This is a nightly-only experimental API. (lazy_cell
)
pub const fn new(f: F) -> LazyCell<T, F>
lazy_cell
)Creates a new lazy value with the given initializing function.
Examples
#![feature(lazy_cell)]
use std::cell::LazyCell;
let hello = "Hello, World!".to_string();
let lazy = LazyCell::new(|| hello.to_uppercase());
assert_eq!(&*lazy, "HELLO, WORLD!");
sourcepub fn force(this: &LazyCell<T, F>) -> &T
🔬This is a nightly-only experimental API. (lazy_cell
)
pub fn force(this: &LazyCell<T, F>) -> &T
lazy_cell
)Forces the evaluation of this lazy value and returns a reference to the result.
This is equivalent to the Deref
impl, but is explicit.
Examples
#![feature(lazy_cell)]
use std::cell::LazyCell;
let lazy = LazyCell::new(|| 92);
assert_eq!(LazyCell::force(&lazy), &92);
assert_eq!(&*lazy, &92);