Struct std::lazy::SyncLazy[−][src]

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")
}
Run

Implementations

impl<T, F> SyncLazy<T, F>[src]

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

🔬 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>[src]

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

Notable traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]

🔬 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);
Run

Trait Implementations

impl<T: Debug, F> Debug for SyncLazy<T, F>[src]

impl<T: Default> Default for SyncLazy<T>[src]

fn default() -> SyncLazy<T>[src]

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

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

type Target = T

The resulting type after dereferencing.

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

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

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

Auto Trait Implementations

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

impl<T, F> Unpin for SyncLazy<T, F> where
    F: Unpin,
    T: Unpin, 

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized, [src]

impl<T> Borrow<T> for T where
    T: ?Sized, [src]

impl<T> BorrowMut<T> for T where
    T: ?Sized, [src]

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, [src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, [src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, [src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.