Struct Current 

pub struct Current<T> { /* private fields */ }

Holds a value when entered or nothing when not.

Implementations

impl<T> Current<T>

pub const fn new() -> Self

Construct a new (empty) instance.

pub fn enter<F, R>( this: &'static LocalKey<Self>, enter: &mut Enter, value: T, f: F, ) -> R

where F: FnOnce(&mut Enter) -> R,

Set instance to value while running the callback.

On exit the instance is cleared.

Panics

Panics if the instance already was entered.

pub fn with<F, R>(this: &'static LocalKey<Self>, f: F) -> R

where F: FnOnce(Option<&T>) -> R,

Run callback with a reference to the current value (if there is one)

The callback will be called while holding a shareable lock to the inner value.

Panics

Panics if the inner value is currently locked exclusively by a with_mut call.

pub fn with_mut<F, R>(this: &'static LocalKey<Self>, f: F) -> R

where F: FnOnce(Option<&mut T>) -> R,

Run callback with a reference to the current value (if there is one)

The callback will be called while holding an exclusive lock to the inner value.

Panics

Panics if the inner value is currently locked by a with or a with_mut call.

Trait Implementations

impl<T: Debug> Debug for Current<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.