pub struct LazyLock<T, F = fn() -> T> { /* private fields */ }
🔬This is a nightly-only experimental API. (
once_cell
#74465)Expand description
A value which is initialized on the first access.
This type is a thread-safe LazyCell
, and can be used in statics.
Examples
#![feature(once_cell)]
use std::collections::HashMap;
use std::sync::LazyLock;
static HASHMAP: LazyLock<HashMap<i32, String>> = LazyLock::new(|| {
println!("initializing");
let mut m = HashMap::new();
m.insert(13, "Spica".to_string());
m.insert(74, "Hoyten".to_string());
m
});
fn main() {
println!("ready");
std::thread::spawn(|| {
println!("{:?}", HASHMAP.get(&13));
}).join().unwrap();
println!("{:?}", HASHMAP.get(&74));
// Prints:
// ready
// initializing
// Some("Spica")
// Some("Hoyten")
}
Run