Enum AsyncValue 

pub enum AsyncValue<T> {
    Idle,
    Loading(Option<T>),
    Ready(T),
    Error(Arc<dyn Error + Sync + Send>),
}

The heavy-work idiom: AsyncValue state, use_task (the blessed load/compute helper), UseTask handle, and spawn_blocking (the CPU-bound entry point) — Frust’s counterpart to Flutter’s compute()/FutureBuilder, with explicit cancellation on component teardown. spawn_blocking joins the existing spawn/spawn_local routing pair (async IO / UI-thread !Send / one-off CPU work). App crates need no new dependency: this is the whole heavy-work surface. See frust_reactive::task for the threading contract. The exhaustive state of an asynchronously-loaded value.

Deliberately named for parity with Riverpod’s AsyncValue<T> (Flutter) — the genuine prior art for a load/data/error sum type with exhaustive matching (research §9). The four states are:

• Idle — nothing requested yet.
• Loading — a fetch is in flight. It carries the previous value (Some on a refresh, None on a first load), so a UI can keep showing stale data instead of flickering to a spinner — mirroring Riverpod’s copyWithPrevious.
• Ready — the fetch resolved to a value.
• Error — the fetch failed.

Variants

Idle

No fetch requested yet.

Loading(Option<T>)

A fetch is in flight; carries the previous value for refresh-without-flicker (None on a first load).

Ready(T)

The fetch resolved.

Error(Arc<dyn Error + Sync + Send>)

The fetch failed.

Implementations

impl<T> AsyncValue<T>

pub fn is_idle(&self) -> bool

Whether this is Idle.

pub fn is_loading(&self) -> bool

Whether a fetch is in flight.

pub fn is_ready(&self) -> bool

Whether the fetch resolved to a value.

pub fn is_error(&self) -> bool

Whether the fetch failed.

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

The resolved value, if Ready.

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

The best-available value: the resolved one when Ready, or the carried-over previous one while Loading a refresh. This is what a flicker-free UI reads.

pub fn error(&self) -> Option<&Arc<dyn Error + Sync + Send>>

The error, if Error.

Trait Implementations

impl<T> Clone for AsyncValue<T>

where T: Clone,

fn clone(&self) -> AsyncValue<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> Debug for AsyncValue<T>

where T: Debug,

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

Formats the value using the given formatter.

impl<T> Default for AsyncValue<T>

fn default() -> AsyncValue<T>

Returns the “default value” for a type.