std::sync::OnceState - Rust
Description: API documentation for the Rust `OnceState` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, OnceState

# Struct std::sync::OnceState [−] [src]

    pub struct OnceState { /* fields omitted */ }

🔬 This is a nightly-only experimental API. (`once_poison` #33577)

State yielded to `call_once_force`’s closure parameter. The state can be used to query the poison status of the `Once`.

## Methods

### `impl OnceState`
[src]

#### `pub fn poisoned(&self) -> bool`
[src]

🔬 This is a nightly-only experimental API. (`once_poison` #33577)

Returns whether the associated `Once` was poisoned prior to the invocation of the closure passed to `call_once_force`.

# Examples

A poisoned `Once`:

    #![feature(once_poison)]

    use std::sync::{Once, ONCE_INIT};
    use std::thread;

    static INIT: Once = ONCE_INIT;

    // poison the once
    let handle = thread::spawn(|| {
        INIT.call_once(|| panic!());
    });
    assert!(handle.join().is_err());

    INIT.call_once_force(|state| {
        assert!(state.poisoned());
    });Run

An unpoisoned `Once`:

    #![feature(once_poison)]

    use std::sync::{Once, ONCE_INIT};

    static INIT: Once = ONCE_INIT;

    INIT.call_once_force(|state| {
        assert!(!state.poisoned());
    });Run

## Trait Implementations

### `impl Debug for OnceState`
[src]

#### `fn fmt(&self, __arg_0: &mut Formatter) -> Result`
[src]

Formats the value using the given formatter. Read more

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