pub struct Lazy<T, F = fn() -> T> { /* fields omitted */ }
🔬 This is a nightly-only experimental API. (
once_cell
#74465)
Expand description
A value which is initialized on the first access.
#![feature(once_cell)]
use std::lazy::Lazy;
let lazy: Lazy<i32> = Lazy::new(|| {
println!("initializing");
92
});
println!("ready");
println!("{}", *lazy);
println!("{}", *lazy);
Run
🔬 This is a nightly-only experimental API. (
once_cell
#74465)
Creates a new lazy value with the given initializing function.
#![feature(once_cell)]
use std::lazy::Lazy;
let hello = "Hello, World!".to_string();
let lazy = Lazy::new(|| hello.to_uppercase());
assert_eq!(&*lazy, "HELLO, WORLD!");
Run
🔬 This is a nightly-only experimental API. (
once_cell
#74465)
Forces the evaluation of this lazy value and returns a reference to
the result.
This is equivalent to the Deref
impl, but is explicit.
#![feature(once_cell)]
use std::lazy::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force(&lazy), &92);
assert_eq!(&*lazy, &92);
Run
Formats the value using the given formatter. Read more
Creates a new lazy value using Default
as the initializing function.
The resulting type after dereferencing.
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
The type returned in the event of a conversion error.
The type returned in the event of a conversion error.