fs2-core/fs2.concurrent/SignallingRef

SignallingRef

abstract class SignallingRef[F <: ([_$6] =>> Any), A] extends Ref[F, A] with Signal[F, A]
Pure holder of a single value of type A that can be both read
and updated in the effect F.
The update methods have the same semantics as Ref, as well as
propagating changes to discrete (with a last-update-wins policy
in case of very fast updates).
The access method differs slightly from Ref in that the update
function, in the presence of discrete, can return false and
need looping even without any other writers.
Companion
object
trait Signal[F, A]
class Ref[F, A]
trait RefSink[F, A]
trait RefSource[F, A]
class Object
trait Matchable
class Any

Value members

Inherited methods

def set(a: A): F[Unit]
Sets the current value to a.
The returned action completes after the reference has been successfully set.
Satisfies:
r.set(fa) *> r.get == fa
Inhertied from
RefSink
def updateAndGet(f: A => A): F[A]
Updates the current value using f, and returns the updated value.
Inhertied from
Ref
def modifyState[B](state: State[A, B]): F[B]
Like tryModifyState but retries the modification until successful.
Inhertied from
Ref
def tryUpdate(f: A => A): F[Boolean]
Attempts to modify the current value once, returning false if another
concurrent modification completes between the time the variable is
read and the time it is set.
Inhertied from
Ref
def update(f: A => A): F[Unit]
Modifies the current value using the supplied update function. If another modification
occurs between the time the current value is read and subsequently updated, the modification
is retried using the new value. Hence, f may be invoked multiple times.
Satisfies:
r.update(_ => a) == r.set(a)
Inhertied from
Ref
def continuous: Stream[F, A]
Returns a stream of the current value of the signal. An element is always
available -- on each pull, the current value is supplied.
Inhertied from
Signal
def tryModify[B](f: A => (A, B)): F[Option[B]]
Like tryUpdate but allows the update function to return an output value of
type B. The returned action completes with None if the value is not updated
successfully and Some(b) otherwise.
Inhertied from
Ref
def getAndSet(a: A): F[A]
Replaces the current value with a, returning the previous value.
Inhertied from
Ref
def tryModifyState[B](state: State[A, B]): F[Option[B]]
Update the value of this ref with a state computation.
The current value of this ref is used as the initial state and the computed output state
is stored in this ref after computation completes. If a concurrent modification occurs,
None is returned.
Inhertied from
Ref
def get: F[A]
Asynchronously gets the current value of this Signal.
Inhertied from
Signal
def access: F[(A, A => F[Boolean])]
Obtains a snapshot of the current value, and a setter for updating it.
The setter may noop (in which case false is returned) if another concurrent
call to access uses its setter first.
Once it has noop'd or been used once, a setter never succeeds again.
Satisfies:
r.access.map(_._1) == r.get
r.access.flatMap { case (v, setter) => setter(f(v)) } == r.tryUpdate(f).map(_.isDefined)
Inhertied from
Ref
def mapK[G <: ([_$3] =>> Any)](f: FunctionK[F, G])(F: Functor[F]): Ref[G, A]
Modify the context F using transformation f.
Inhertied from
Ref
def getAndUpdate(f: A => A): F[A]
Updates the current value using f and returns the previous value.
In case of retries caused by concurrent modifications,
the returned value will be the last one before a successful update.
Inhertied from
Ref
def discrete: Stream[F, A]
Returns a stream of the updates to this signal.
Updates that are very close together may result in only the last update appearing
in the stream. If you want to be notified about every single update, use
a Queue or Channel instead.
Inhertied from
Signal
def modify[B](f: A => (A, B)): F[B]
Like tryModify but does not complete until the update has been successfully made.
Inhertied from
Ref