Struct std::lazy::SyncOnceCell [−][src]
pub struct SyncOnceCell<T> { /* fields omitted */ }A synchronization primitive which can be written to only once.
This type is a thread-safe OnceCell.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; static CELL: SyncOnceCell<String> = SyncOnceCell::new(); assert!(CELL.get().is_none()); std::thread::spawn(|| { let value: &String = CELL.get_or_init(|| { "Hello, World!".to_string() }); assert_eq!(value, "Hello, World!"); }).join().unwrap(); let value: Option<&String> = CELL.get(); assert!(value.is_some()); assert_eq!(value.unwrap().as_str(), "Hello, World!");Run
Implementations
impl<T> SyncOnceCell<T>[src]
impl<T> SyncOnceCell<T>[src]pub const fn new() -> SyncOnceCell<T>[src]
Creates a new empty cell.
pub fn get(&self) -> Option<&T>[src]
Gets the reference to the underlying value.
Returns None if the cell is empty, or being initialized. This
method never blocks.
pub fn get_mut(&mut self) -> Option<&mut T>[src]
Gets the mutable reference to the underlying value.
Returns None if the cell is empty. This method never blocks.
pub fn set(&self, value: T) -> Result<(), T>[src]
Sets the contents of this cell to value.
May block if another thread is currently attempting to initialize the cell. The cell is guaranteed to contain a value when set returns, though not necessarily the one provided.
Returns Ok(()) if the cell’s value was set by this call.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; static CELL: SyncOnceCell<i32> = SyncOnceCell::new(); fn main() { assert!(CELL.get().is_none()); std::thread::spawn(|| { assert_eq!(CELL.set(92), Ok(())); }).join().unwrap(); assert_eq!(CELL.set(62), Err(62)); assert_eq!(CELL.get(), Some(&92)); }Run
pub fn get_or_init<F>(&self, f: F) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W where
F: FnOnce() -> T, [src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut WF: FnOnce() -> T,
Gets the contents of the cell, initializing it with f if the cell
was empty.
Many threads may call get_or_init concurrently with different
initializing functions, but it is guaranteed that only one function
will be executed.
Panics
If f panics, the panic is propagated to the caller, and the cell
remains uninitialized.
It is an error to reentrantly initialize the cell from f. The
exact outcome is unspecified. Current implementation deadlocks, but
this may be changed to a panic in the future.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell = SyncOnceCell::new(); let value = cell.get_or_init(|| 92); assert_eq!(value, &92); let value = cell.get_or_init(|| unreachable!()); assert_eq!(value, &92);Run
pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E> where
F: FnOnce() -> Result<T, E>, [src]
F: FnOnce() -> Result<T, E>,
Gets the contents of the cell, initializing it with f if
the cell was empty. If the cell was empty and f failed, an
error is returned.
Panics
If f panics, the panic is propagated to the caller, and
the cell remains uninitialized.
It is an error to reentrantly initialize the cell from f.
The exact outcome is unspecified. Current implementation
deadlocks, but this may be changed to a panic in the future.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell = SyncOnceCell::new(); assert_eq!(cell.get_or_try_init(|| Err(())), Err(())); assert!(cell.get().is_none()); let value = cell.get_or_try_init(|| -> Result<i32, ()> { Ok(92) }); assert_eq!(value, Ok(&92)); assert_eq!(cell.get(), Some(&92))Run
pub fn into_inner(self) -> Option<T>[src]
Consumes the SyncOnceCell, returning the wrapped value. Returns
None if the cell was empty.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let cell: SyncOnceCell<String> = SyncOnceCell::new(); assert_eq!(cell.into_inner(), None); let cell = SyncOnceCell::new(); cell.set("hello".to_string()).unwrap(); assert_eq!(cell.into_inner(), Some("hello".to_string()));Run
pub fn take(&mut self) -> Option<T>[src]
Takes the value out of this SyncOnceCell, moving it back to an uninitialized state.
Has no effect and returns None if the SyncOnceCell hasn’t been initialized.
Safety is guaranteed by requiring a mutable reference.
Examples
#![feature(once_cell)] use std::lazy::SyncOnceCell; let mut cell: SyncOnceCell<String> = SyncOnceCell::new(); assert_eq!(cell.take(), None); let mut cell = SyncOnceCell::new(); cell.set("hello".to_string()).unwrap(); assert_eq!(cell.take(), Some("hello".to_string())); assert_eq!(cell.get(), None);Run
Trait Implementations
impl<T: Clone> Clone for SyncOnceCell<T>[src]
impl<T: Clone> Clone for SyncOnceCell<T>[src]fn clone(&self) -> SyncOnceCell<T>[src]
pub fn clone_from(&mut self, source: &Self)1.0.0[src]
impl<T> Default for SyncOnceCell<T>[src]
impl<T> Default for SyncOnceCell<T>[src]fn default() -> SyncOnceCell<T>[src]
impl<T> Drop for SyncOnceCell<T>[src]
impl<T> Drop for SyncOnceCell<T>[src]impl<T> From<T> for SyncOnceCell<T>[src]
impl<T> From<T> for SyncOnceCell<T>[src]impl<T: PartialEq> PartialEq<SyncOnceCell<T>> for SyncOnceCell<T>[src]
impl<T: PartialEq> PartialEq<SyncOnceCell<T>> for SyncOnceCell<T>[src]impl<T: Eq> Eq for SyncOnceCell<T>[src]
impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for SyncOnceCell<T>[src]
impl<T: Send> Send for SyncOnceCell<T>[src]
impl<T: Sync + Send> Sync for SyncOnceCell<T>[src]
impl<T: UnwindSafe> UnwindSafe for SyncOnceCell<T>[src]
Auto Trait Implementations
impl<T> Unpin for SyncOnceCell<T> where
T: Unpin,
T: Unpin,
Blanket Implementations
impl<T> Borrow<T> for T where
T: ?Sized, [src]
impl<T> Borrow<T> for T where
T: ?Sized, [src]pub fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut Wimpl<T> BorrowMut<T> for T where
T: ?Sized, [src]
impl<T> BorrowMut<T> for T where
T: ?Sized, [src]pub fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W