Struct Observable 

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

A shared, version-tracked value with change notification.

Cloning an Observable creates a new handle to the same inner state — both handles see the same value and share subscribers.

Invariants

1. version increments by exactly 1 on each value-changing mutation.
2. set(v) where v == current is a no-op.
3. Subscribers are notified in registration order.
4. Dead subscribers (dropped Subscription guards) are pruned lazily.

Implementations

impl<T: Clone + PartialEq + 'static> Observable<T>

pub fn new(value: T) -> Self

Create a new observable with the given initial value.

The initial version is 0 and no subscribers are registered.

pub fn get(&self) -> T

Get a clone of the current value.

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

Access the current value by reference without cloning.

The closure f receives an immutable reference to the value.

pub fn set(&self, value: T)

Set a new value. If the new value differs from the current value (by PartialEq), the version is incremented and all live subscribers are notified.

This method is safe to call re-entrantly from within subscriber callbacks.

pub fn update(&self, f: impl FnOnce(&mut T))

Modify the value in place via a closure. If the value changes (compared by PartialEq against a snapshot), the version is incremented and subscribers are notified.

This method is safe to call re-entrantly from within subscriber callbacks.

pub fn subscribe(&self, callback: impl Fn(&T) + 'static) -> Subscription

Subscribe to value changes. The callback is invoked with a reference to the new value each time it changes.

Returns a Subscription guard. Dropping the guard unsubscribes the callback (it will not be called after drop, though it may still be in the subscriber list until the next notify() prunes it).

pub fn version(&self) -> u64

Current version number. Increments by 1 on each value-changing mutation. Useful for dirty-checking in render loops.

pub fn subscriber_count(&self) -> usize

Number of currently registered subscribers (including dead ones not yet pruned).

Trait Implementations

impl<T> Clone for Observable<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: Debug> Debug for Observable<T>

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

Formats the value using the given formatter.