| commit | 24b33bc54334e8b8fca9badb02cddad3ffa33069 | [log] [tgz] |
|---|---|---|
| author | Jeff Vander Stoep <[email protected]> | Fri Feb 17 08:46:35 2023 +0000 |
| committer | Automerger Merge Worker <[email protected]> | Fri Feb 17 08:46:35 2023 +0000 |
| tree | f0df62c2365cf1af4985701b56e920f31df686ec | |
| parent | 9c965f3e81228a1aa52e793ae9ed2a7a6d699bb6 [diff] | |
| parent | c82e56c12cc39d4be674988d184c4e393f99fdc8 [diff] |
Upgrade once_cell to 1.17.1 am: 1da3db55c9 am: a4ccd08bab am: c82e56c12c Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/once_cell/+/2440588 Change-Id: I556c183aff39edb19c4d601c59bffeb044bd1c07 Signed-off-by: Automerger Merge Worker <[email protected]>
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:
impl OnceCell<T> { fn new() -> OnceCell<T> { ... } fn set(&self, value: T) -> Result<(), T> { ... } fn get(&self) -> Option<&T> { ... } }
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 std::{sync::Mutex, collections::HashMap}; use once_cell::sync::Lazy; static GLOBAL_DATA: Lazy<Mutex<HashMap<i32, String>>> = Lazy::new(|| { let mut m = HashMap::new(); m.insert(13, "Spica".to_string()); m.insert(74, "Hoyten".to_string()); Mutex::new(m) }); fn main() { println!("{:?}", GLOBAL_DATA.lock().unwrap()); }
More patterns and use-cases are in the docs!
The API of once_cell is being proposed for inclusion in std.