[][src]Struct once_cell::sync::Lazy

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

A value which is initialized on the first access.

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


use std::collections::HashMap;

use once_cell::sync::Lazy;

static HASHMAP: Lazy<HashMap<i32, String>> = Lazy::new(|| {
    let mut m = HashMap::new();
    m.insert(13, "Spica".to_string());
    m.insert(74, "Hoyten".to_string());

fn main() {
    std::thread::spawn(|| {
        println!("{:?}", HASHMAP.get(&13));
    println!("{:?}", HASHMAP.get(&74));

    // Prints:
    //   ready
    //   initializing
    //   Some("Spica")
    //   Some("Hoyten")


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

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

Creates a new lazy value with the given initializing function.

impl<T, F: FnOnce() -> T> Lazy<T, F>[src]

pub fn force(this: &Lazy<T, F>) -> &T[src]

Forces the evaluation of this lazy value and returns a reference to the 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);

Trait Implementations

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

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

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

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

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

type Target = T

The resulting type after dereferencing.

impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F>[src]

impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where
    OnceCell<T>: RefUnwindSafe

impl<T, F: Send> Sync for Lazy<T, F> where
    OnceCell<T>: Sync

Auto Trait Implementations

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

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

impl<T, F> UnwindSafe for Lazy<T, F> where
    F: UnwindSafe,
    T: UnwindSafe

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized

impl<T> Borrow<T> for T where
    T: ?Sized

impl<T> BorrowMut<T> for T where
    T: ?Sized

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

impl<T, U> Into<U> for T where
    U: From<T>, 

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 

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

The type returned in the event of a conversion error.