Type Alias Once 

pub type Once = OnceCell<()>;

A synchronization primitive which can be used to run a one-time global initialization.

This type uses the blocking synchronization mechanism provided by the underlying operating system.

For the API of this type alias, see the generic OnceCell type. This is a specialization with T = ().

Examples

use conquer_once::Once;

static mut GLOBAL: usize = 0;
static INIT: Once = Once::uninit();

fn get_global() -> usize {
    // SAFETY: this is safe because the `Once` ensures the `static mut` is
    // assigned by only one thread and without data races.
    unsafe {
        INIT.init_once(|| {
            GLOBAL = expensive_computation();
        });
        GLOBAL
    }
}

fn expensive_computation() -> usize {
    // ...
}

Aliased Type

pub struct Once { /* private fields */ }