Struct CallbackSlot 

pub struct CallbackSlot<T: 'static> { /* private fields */ }

Available on crate feature embedded_runtime only.

An address-stable slot holding a caller-provided callback for the duration of a run, backing an output (or network-out) parameter of a generated embedded function.

The flow side holds a sink closure (created via sink) that forwards each emitted item to whatever callback is currently installed. The application side temporarily installs a callback around each run via invoke_with:

slot.invoke_with(&mut |item| results.push(item), || flow.run_available_sync());

Items emitted while no callback is installed are silently dropped.

Implementations

impl<T: 'static> CallbackSlot<T>

pub const fn new() -> Self

Creates a slot with no callback installed.

pub unsafe fn sink(self: Pin<&Self>) -> impl FnMut(T) + use<T>

Creates a sink closure that forwards each item to the currently-installed callback, for passing to a generated embedded function.

Safety

The slot must outlive the returned closure. (The slot cannot move while the closure exists, which is guaranteed by self being pinned, and the closure cannot be sent to another thread, as it is !Send.)

pub fn invoke(&self, item: T)

Invokes the currently-installed callback with item, or drops item if no callback is installed.

The callback is moved out of the slot while it runs (and restored afterwards, even on panic), so a re-entrant invocation of the same slot finds it empty and drops its item, rather than aliasing the already-running callback.

pub fn invoke_with<R>( &self, callback: &mut dyn FnMut(T), f: impl FnOnce() -> R, ) -> R

Installs callback for the duration of f, then restores whatever was previously installed — even if f panics. Items the flow emits to this slot while f runs are passed to callback.

Calls may be nested (e.g. to install callbacks on several slots around a single run); the innermost installation wins for its duration.

Trait Implementations

impl<T: 'static> Debug for CallbackSlot<T>

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

Formats the value using the given formatter.

impl<T: 'static> Default for CallbackSlot<T>

fn default() -> Self

Returns the “default value” for a type.