Struct Computed 

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

A lazily-evaluated, memoized value derived from one or more Observable dependencies.

Cloning a Computed creates a new handle to the same inner state.

Invariants

1. dirty is true after any dependency changes and before get().
2. version increments by 1 on each recomputation.
3. The compute function is called only when dirty is true and get() is called.

Implementations

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

pub fn from_observable<S: Clone + PartialEq + 'static>( source: &Observable<S>, map: impl Fn(&S) -> T + 'static, ) -> Self

Create a computed value derived from a single observable.

The map function receives a reference to the source value and returns the derived value.

pub fn from2<S1, S2>( s1: &Observable<S1>, s2: &Observable<S2>, map: impl Fn(&S1, &S2) -> T + 'static, ) -> Self

where S1: Clone + PartialEq + 'static, S2: Clone + PartialEq + 'static,

Create a computed value derived from two observables.

pub fn from3<S1, S2, S3>( s1: &Observable<S1>, s2: &Observable<S2>, s3: &Observable<S3>, map: impl Fn(&S1, &S2, &S3) -> T + 'static, ) -> Self

where S1: Clone + PartialEq + 'static, S2: Clone + PartialEq + 'static, S3: Clone + PartialEq + 'static,

Create a computed value derived from three observables.

pub fn from_fn( compute: impl Fn() -> T + 'static, subscriptions: Vec<Subscription>, ) -> Self

Create a computed value from a standalone compute function and pre-built subscriptions.

This is the low-level constructor for advanced use cases where the caller manages dependency subscriptions manually.

pub fn get(&self) -> T

Get the current value, recomputing if any dependency has changed.

Returns a clone of the cached value. If the value is dirty, the compute function is called first and the result is cached.

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

Access the current value by reference without cloning.

Forces recomputation if dirty. The closure receives an immutable reference to the cached value.

Panics

Panics if the closure attempts to call get() on the same Computed (re-entrant borrow).

pub fn is_dirty(&self) -> bool

Whether the cached value is stale.

pub fn invalidate(&self)

Force invalidation of the cached value. The next get() will recompute.

pub fn version(&self) -> u64

Current version number. Increments by 1 on each recomputation.

Trait Implementations

impl<T> Clone for Computed<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 Computed<T>

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

Formats the value using the given formatter.