Struct std::lazy::SyncLazy

pub struct SyncLazy<T, F = fn() -> T> { /* fields omitted */ }

🔬 This is a nightly-only experimental API. (once_cell #74465)

A value which is initialized on the first access.

This type is a thread-safe Lazy, and can be used in statics.

Examples

#![feature(once_cell)]

use std::collections::HashMap;

use std::lazy::SyncLazy;

static HASHMAP: SyncLazy<HashMap<i32, String>> = SyncLazy::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")
}

Implementations

impl<T, F> SyncLazy<T, F>

pub const fn new(f: F) -> SyncLazy<T, F>

🔬 This is a nightly-only experimental API. (once_cell #74465)

Creates a new lazy value with the given initializing function.

impl<T, F: FnOnce() -> T> SyncLazy<T, F>

pub fn force(this: &SyncLazy<T, F>) -> &T

🔬 This is a nightly-only experimental API. (once_cell #74465)

Forces the evaluation of this lazy value and returns a reference to result. This is equivalent to the Deref impl, but is explicit.

Examples

#![feature(once_cell)]

use std::lazy::SyncLazy;

let lazy = SyncLazy::new(|| 92);

assert_eq!(SyncLazy::force(&lazy), &92);
assert_eq!(&*lazy, &92);

Trait Implementations

impl<T: Debug, F> Debug for SyncLazy<T, F>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for SyncLazy<T>

fn default() -> SyncLazy<T>

Creates a new lazy value using Default as the initializing function.

impl<T, F: FnOnce() -> T> Deref for SyncLazy<T, F>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T, F: UnwindSafe> RefUnwindSafe for SyncLazy<T, F> where
    SyncOnceCell<T>: RefUnwindSafe, 

impl<T, F: Send> Sync for SyncLazy<T, F> where
    SyncOnceCell<T>: Sync, 

impl<T, F: UnwindSafe> UnwindSafe for SyncLazy<T, F> where
    SyncOnceCell<T>: UnwindSafe,