Overview
once_cell
provides two new cell-like types, unsync::OnceCell
and sync::OnceCell
. OnceCell
might store arbitrary non-Copy
types, can be assigned to at most once and provide direct access
to the stored contents. In a nutshell, API looks roughly like this:
Note that, like with RefCell
and Mutex
, the set
method requires only a shared reference.
Because of the single assignment restriction get
can return an &T
instead of Ref<T>
or MutexGuard<T>
.
once_cell
also has a Lazy<T>
type, build on top of OnceCell
which provides the same API as
the lazy_static!
macro, but without using any macros:
use ;
use Lazy;
static GLOBAL_DATA: = new;
More patterns and use-cases are in the docs!
Related crates
- double-checked-cell
- lazy-init
- lazycell
- mitochondria
- lazy_static
- async_once_cell
- generic_once_cell (bring your own mutex)
The API of once_cell
is being proposed for inclusion in
std
.