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| -rw-r--r-- | library/core/src/cell.rs | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs index ac026de95da..6cdc1e00f47 100644 --- a/library/core/src/cell.rs +++ b/library/core/src/cell.rs @@ -82,6 +82,20 @@ //! //! The corresponding [`Sync`] version of `OnceCell<T>` is [`OnceLock<T>`]. //! +//! ## `LazyCell<T, F>` +//! +//! A common pattern with OnceCell is, for a given OnceCell, to use the same function on every +//! call to [`OnceCell::get_or_init`] with that cell. This is what is offered by [`LazyCell`], +//! which pairs cells of `T` with functions of `F`, and always calls `F` before it yields `&T`. +//! This happens implicitly by simply attempting to dereference the LazyCell to get its contents, +//! so its use is much more transparent with a place which has been initialized by a constant. +//! +//! More complicated patterns that don't fit this description can be built on `OnceCell<T>` instead. +//! +//! `LazyCell` works by providing an implementation of `impl Deref` that calls the function, +//! so you can just use it by dereference (e.g. `*lazy_cell` or `lazy_cell.deref()`). +//! +//! The corresponding [`Sync`] version of `LazyCell<T, F>` is [`LazyLock<T, F>`]. //! //! # When to choose interior mutability //! @@ -230,6 +244,7 @@ //! [`RwLock<T>`]: ../../std/sync/struct.RwLock.html //! [`Mutex<T>`]: ../../std/sync/struct.Mutex.html //! [`OnceLock<T>`]: ../../std/sync/struct.OnceLock.html +//! [`LazyLock<T, F>`]: ../../std/sync/struct.LazyLock.html //! [`Sync`]: ../../std/marker/trait.Sync.html //! [`atomic`]: crate::sync::atomic |