Struct double_checked_cell_async::DoubleCheckedCell

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

A thread-safe lazily initialized cell.

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

Methods

impl<T> DoubleCheckedCell<T>

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);

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"));

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);

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));

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));

Trait Implementations

impl<T: Debug> Debug for DoubleCheckedCell<T>

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

Formats the value using the given formatter.

impl<T> Default for DoubleCheckedCell<T>

fn default() -> DoubleCheckedCell<T>

Returns the "default value" for a type.

impl<T> From<T> for DoubleCheckedCell<T>

fn from(t: T) -> DoubleCheckedCell<T>

Performs the conversion.

impl<T> RefUnwindSafe for DoubleCheckedCell<T>

impl<T: Send + Sync> Sync for DoubleCheckedCell<T>