Struct State 

pub struct State<T: Clone + 'static> { /* private fields */ }

Cheap copyable read-only view of a state cell.

Implementations

impl<T: Clone + 'static> State<T>

pub fn is_alive(&self) -> bool

pub fn try_with<R>(&self, f: impl FnOnce(&T) -> R) -> Option<R>

pub fn try_value(&self) -> Option<T>

pub fn with<R>(&self, f: impl FnOnce(&T) -> R) -> R

pub fn value(&self) -> T

pub fn get(&self) -> T

pub fn has_subscribers(&self) -> bool

pub fn on_subscriber(&self, callback: Rc<dyn Fn()>)

pub fn subscription_hold(&self) -> StateSubscriptionHold

Counts this state as subscribed for as long as the returned guard lives, without observing it from any scope.

Snapshot observers subscribe reads made under composition or the draw phase, and producers gated on State::has_subscribers — an infinite transition, for one — stop themselves when the last such subscriber leaves. A consumer that reads the value from a polling context (a frame effect stepping it into a derived state, a background task) is invisible to that accounting and would starve the producer it depends on. Holding this guard keeps the producer alive; dropping it releases the count.

Trait Implementations

impl<T: Clone + 'static> Clone for State<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Clone + 'static> Copy for State<T>

impl<T: Debug + Clone + 'static> Debug for State<T>

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

Formats the value using the given formatter.

impl<T: Clone + 'static> Eq for State<T>

impl<T: Clone + 'static> PartialEq for State<T>

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.