Struct DoubleCheckedCell

Source

pub struct DoubleCheckedCell<T> { /* private fields */ }

Expand description

A thread-safe lazily initialized cell.

The cell is immutable once it is initialized. See the module-level documentation for more.

Implementations§

Source §

impl<T> DoubleCheckedCell<T>

Source

pub fn new() -> DoubleCheckedCell<T>

Creates a new uninitialized DoubleCheckedCell.

§Examples

use double_checked_cell::DoubleCheckedCell;

let cell = DoubleCheckedCell::<u32>::new();
assert_eq!(cell.get().await, None);

Source

pub async fn get(&self) -> Option<&T>

Borrows the value if the cell is initialized.

§Examples

use double_checked_cell::DoubleCheckedCell;

let cell = DoubleCheckedCell::from("hello");
assert_eq!(cell.get().await, Some(&"hello"));

Source

pub async fn get_or_init<Fut>(&self, init: Fut) -> &T
where Fut: Future<Output = T>,

Borrows the value if the cell is initialized or initializes it from a closure.

§Panics

Panics or deadlocks when trying to access the cell from the initilization closure.

§Examples

use double_checked_cell::DoubleCheckedCell;
use futures::future::ready;

let cell = DoubleCheckedCell::new();

// Initialize the cell.
let value = cell.get_or_init(async { 1 + 2 }).await;
assert_eq!(*value, 3);

// The cell is now immutable.
let value = cell.get_or_init(async { 42 }).await;
assert_eq!(*value, 3);

Source

pub async fn get_or_try_init<Fut, E>(&self, init: Fut) -> Result<&T, E>
where Fut: Future<Output = Result<T, E>>,

Borrows the value if the cell is initialized or attempts to initialize it from a closure.

§Errors

Forwards any error from the closure if the cell is not yet initialized. The cell then remains uninitialized.

§Panics

Panics or deadlocks when trying to access the cell from the initilization closure.

§Examples

use double_checked_cell::DoubleCheckedCell;
use futures::future::ready;

let cell = DoubleCheckedCell::new();

let result = cell.get_or_try_init(async { "not an integer".parse() }).await;
assert!(result.is_err());

let result = cell.get_or_try_init(async { "42".parse() }).await;
assert_eq!(result, Ok(&42));

let result = cell.get_or_try_init(async { "irrelevant".parse() }).await;
assert_eq!(result, Ok(&42));

Source

pub fn into_inner(self) -> Option<T>

Unwraps the value.

§Examples

use double_checked_cell::DoubleCheckedCell;

let cell = DoubleCheckedCell::from(42);
let contents = cell.into_inner();
assert_eq!(contents, Some(42));