pub struct LazyLock<T, F = fn() -> T> {
once: Once,
data: UnsafeCell<Data<T, F>>,
}
🔬This is a nightly-only experimental API. (
lazy_cell
#109736)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(lazy_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")
}
RunFields§
§once: Once
🔬This is a nightly-only experimental API. (
§lazy_cell
#109736)data: UnsafeCell<Data<T, F>>
🔬This is a nightly-only experimental API. (
lazy_cell
#109736)Implementations§
source§impl<T, F: FnOnce() -> T> LazyLock<T, F>
impl<T, F: FnOnce() -> T> LazyLock<T, F>
sourcepub const fn new(f: F) -> LazyLock<T, F>
🔬This is a nightly-only experimental API. (lazy_cell
#109736)
pub const fn new(f: F) -> LazyLock<T, F>
lazy_cell
#109736)Creates a new lazy value with the given initializing function.
sourcepub fn into_inner(this: Self) -> Result<T, F>
🔬This is a nightly-only experimental API. (lazy_cell_consume
#109736)
pub fn into_inner(this: Self) -> Result<T, F>
lazy_cell_consume
#109736)Consumes this LazyLock
returning the stored value.
Returns Ok(value)
if Lazy
is initialized and Err(f)
otherwise.
Examples
#![feature(lazy_cell)]
#![feature(lazy_cell_consume)]
use std::sync::LazyLock;
let hello = "Hello, World!".to_string();
let lazy = LazyLock::new(|| hello.to_uppercase());
assert_eq!(&*lazy, "HELLO, WORLD!");
assert_eq!(LazyLock::into_inner(lazy).ok(), Some("HELLO, WORLD!".to_string()));
RunTrait Implementations§
impl<T: RefUnwindSafe + UnwindSafe, F: UnwindSafe> RefUnwindSafe for LazyLock<T, F>
impl<T: Sync + Send, F: Send> Sync for LazyLock<T, F>
impl<T: UnwindSafe, F: UnwindSafe> UnwindSafe for LazyLock<T, F>
Auto Trait Implementations§
impl<T, F> Send for LazyLock<T, F>where F: Send, T: Send,
impl<T, F> Unpin for LazyLock<T, F>where F: Unpin, T: Unpin,
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