pub struct Lazy<T, F: Fn() -> T = fn() -> T> { /* fields omitted */ }
A value which is initialized on the first access.
#[macro_use]
extern crate once_cell;
use std::collections::HashMap;
use once_cell::sync::Lazy;
static HASHMAP: Lazy<HashMap<i32, String>> = sync_lazy! {
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));
}
Creates a new lazy value with the given initializing
function.
Forces the evaluation of this lazy value and
returns a reference to result. This is equivalent
to the Deref
impl, but is explicit.
use once_cell::sync::Lazy;
let lazy = Lazy::new(|| 92);
assert_eq!(Lazy::force(&lazy), &92);
assert_eq!(&*lazy, &92);
Formats the value using the given formatter. Read more
The resulting type after dereferencing.