[][src]Struct std::lazy::Lazy

pub struct Lazy<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.

Examples

#![feature(once_cell)]

use std::lazy::Lazy;

let lazy: Lazy<i32> = Lazy::new(|| {
    println!("initializing");
    92
});
println!("ready");
println!("{}", *lazy);
println!("{}", *lazy);

// Prints:
//   ready
//   initializing
//   92
//   92
Run

Implementations

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

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

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

Creates a new lazy value with the given initializing function.

Examples

#![feature(once_cell)]

use std::lazy::Lazy;

let hello = "Hello, World!".to_string();

let lazy = Lazy::new(|| hello.to_uppercase());

assert_eq!(&*lazy, "HELLO, WORLD!");
Run

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

pub fn force(this: &Lazy<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 the result.

This is equivalent to the Deref impl, but is explicit.

Examples

#![feature(once_cell)]

use std::lazy::Lazy;

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

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

Trait Implementations

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

impl<T> Default for Lazy<T, fn() -> T> where
    T: Default
[src]

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

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

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

type Target = T

The resulting type after dereferencing.

Auto Trait Implementations

impl<T, F = fn() -> T> !RefUnwindSafe for Lazy<T, F>

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

impl<T, F = fn() -> T> !Sync for Lazy<T, F>

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
[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.