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Airstream/com.raquo.airstream/com.raquo.airstream.core/WritableSignal

WritableSignal

com.raquo.airstream.core.WritableSignal
trait WritableSignal[A] extends Signal[A], WritableObservable[A]

Attributes

Graph
Supertypes
trait Signal[A]
trait SignalSource[A]
trait Observable[A]
trait Named
trait Source[A]
class Object
trait Matchable
class Any
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Known subtypes
trait MultiParentSignal[I, O]
class CombineSignalN[A, Out]
class SampleCombineSignalN[A, Out]
trait SingleParentSignal[I, O]
class DebuggerSignal[A]
class DistinctSignal[A]
class MapSignal[I, O]
class DerivedVarSignal[A, B]
class ObservedSignal[A]
class ScanLeftSignal[A, B]
class SignalFromStream[A]
class SplitSignal[M, Input, Output, Key]
class SwitchSignal[A]
class Val[A]
class JsPromiseSignal[A]
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Members list

Value members

Concrete methods

final override protected def fireError(nextError: Throwable, transaction: Transaction): Unit

Attributes

Definition Classes
override protected def fireTry(nextValue: Try[A], transaction: Transaction): Unit

Signal propagates only if its value has changed

Signal propagates only if its value has changed

Attributes

Definition Classes
final override protected def fireValue(nextValue: A, transaction: Transaction): Unit

Attributes

Definition Classes
protected def setCurrentValue(newValue: Try[A]): Unit

Inherited methods

override def addObserver(observer: Observer[A])(implicit owner: Owner): Subscription

Subscribe an external observer to this observable

Subscribe an external observer to this observable

Attributes

Definition Classes
Inherited from:
WritableObservable
def changes[AA >: A](compose: EventStream[A] => EventStream[AA]): Signal[AA]

Modify the Signal's changes, e.g. signal.changes(_.delay(ms = 100))

Modify the Signal's changes, e.g. signal.changes(_.delay(ms = 100))

Alias to composeChanges. See also: composeAll

Value parameters

compose

Note: Must not throw!

Attributes

Inherited from:
Signal
def changes: EventStream[A]

A stream of all values in this signal, excluding the initial value.

A stream of all values in this signal, excluding the initial value.

When re-starting this stream, it emits the signal's new current value if and only if something has caused the signal's value to be updated or re-evaluated while the changes stream was stopped. This way the changes stream stays in sync with the signal even after restarting.

Attributes

Inherited from:
Signal
def compose[B](operator: Signal[A] => Signal[B]): Signal[B]

Value parameters

operator

Note: Must not throw!

Attributes

Inherited from:
Signal
def composeAll[B](changesOperator: EventStream[A] => EventStream[B], initialOperator: Try[A] => Try[B], cacheInitialValue: Boolean): Signal[B]

Modify both the Signal's changes stream, and its initial. Similar to composeChanges, but lets you output a type unrelated to A.

Modify both the Signal's changes stream, and its initial. Similar to composeChanges, but lets you output a type unrelated to A.

Value parameters

changesOperator

Note: Must not throw!

initialOperator

Note: Must not throw!

Attributes

Inherited from:
Signal
def composeChanges[AA >: A](operator: EventStream[A] => EventStream[AA]): Signal[AA]

Modify the Signal's changes stream, e.g. signal.composeChanges(_.delay(ms = 100))

Modify the Signal's changes stream, e.g. signal.composeChanges(_.delay(ms = 100))

Alias to changes(operator). See also: composeAll

Value parameters

operator

Note: Must not throw!

Attributes

Inherited from:
Signal
override def debugWith(debugger: Debugger[A]): Signal[A]

See also debug methods in com.raquo.airstream.debug.DebuggableObservable

See also debug methods in com.raquo.airstream.debug.DebuggableObservable

Attributes

Definition Classes
Inherited from:
Signal
protected def defaultDisplayName: String

This is the method that subclasses override to preserve the user's ability to set custom display names.

This is the method that subclasses override to preserve the user's ability to set custom display names.

Attributes

Inherited from:
Named
final def displayName: String

Attributes

Inherited from:
Named
def distinct: Self[A]

Distinct events (but keep all errors) by == (equals) comparison

Distinct events (but keep all errors) by == (equals) comparison

Attributes

Inherited from:
BaseObservable
def distinctBy(key: A => Any): Self[A]

Distinct events (but keep all errors) by matching key Note: key(event) might be evaluated more than once for each event

Distinct events (but keep all errors) by matching key Note: key(event) might be evaluated more than once for each event

Attributes

Inherited from:
BaseObservable
def distinctByFn(isSame: (A, A) => Boolean): Self[A]

Distinct events (but keep all errors) using a comparison function

Distinct events (but keep all errors) using a comparison function

Attributes

Inherited from:
BaseObservable
def distinctByRef(implicit ev: A <:< AnyRef): Self[A]

Distinct events (but keep all errors) by reference equality (eq)

Distinct events (but keep all errors) by reference equality (eq)

Attributes

Inherited from:
BaseObservable
def distinctErrors(isSame: (Throwable, Throwable) => Boolean): Self[A]

Distinct errors only (but keep all events) using a comparison function

Distinct errors only (but keep all events) using a comparison function

Attributes

Inherited from:
BaseObservable
override def distinctTry(isSame: (Try[A], Try[A]) => Boolean): Signal[A]

Distinct all values (both events and errors) using a comparison function

Distinct all values (both events and errors) using a comparison function

Attributes

Definition Classes
Inherited from:
Signal
final override def equals(obj: Any): Boolean

Airstream may internally use Scala library functions which use == or hashCode for equality, for example List.contains. Comparing observables by structural equality pretty much never makes sense, yet it's not that hard to run into that, all you need is to create a case class subclass, and the Scala compiler will generate a structural-equality equals and hashCode methods for you behind the scenes.

Airstream may internally use Scala library functions which use == or hashCode for equality, for example List.contains. Comparing observables by structural equality pretty much never makes sense, yet it's not that hard to run into that, all you need is to create a case class subclass, and the Scala compiler will generate a structural-equality equals and hashCode methods for you behind the scenes.

To prevent that, we make equals and hashCode methods final, using the default implementation (which is reference equality).

Attributes

Definition Classes
Inherited from:
BaseObservable
def flatMap[B, Inner[_], Output <: (Observable)](project: A => Inner[B])(implicit strategy: SwitchingStrategy[Signal, Inner, Output], allowFlatMap: AllowFlatMap): Output[B]

#WARNING: DO NOT USE THIS METHOD. See https://github.com/raquo/Airstream/#flattening-observables

#WARNING: DO NOT USE THIS METHOD. See https://github.com/raquo/Airstream/#flattening-observables

Attributes

Inherited from:
BaseObservable
def flatMapCustom[B, Inner[_], Output <: (Observable)](project: A => Inner[B])(strategy: FlattenStrategy[Signal, Inner, Output]): Output[B]

Value parameters

project

Note: guarded against exceptions

Attributes

Inherited from:
BaseObservable
def flatMapMerge[B, Inner[_], Output <: (Observable)](project: A => Inner[B])(implicit strategy: MergingStrategy[Signal, Inner, Output]): Output[B]

Value parameters

project

Note: guarded against exceptions

Attributes

Inherited from:
BaseObservable
def flatMapSwitch[B, Inner[_], Output <: (Observable)](project: A => Inner[B])(implicit strategy: SwitchingStrategy[Signal, Inner, Output]): Output[B]

Value parameters

project

Note: guarded against exceptions

Attributes

Inherited from:
BaseObservable
def flatMapTo[B, Inner[_], Output <: (Observable)](s: Inner[B])(implicit strategy: SwitchingStrategy[Signal, Inner, Output]): Output[B]

Alias to flatMapSwitch(_ => s)

Alias to flatMapSwitch(_ => s)

Attributes

Inherited from:
BaseObservable
def flatMapWithStatus[B](innerStream: => EventStream[B]): Self[Status[A, B]]

Shorthand for flatMapWithStatus(_ => innerStream).

Shorthand for flatMapWithStatus(_ => innerStream).

Attributes

Inherited from:
BaseObservable
def flatMapWithStatus[B](project: A => EventStream[B]): Self[Status[A, B]]

Based on flatMapSwitch, but tracks the status of input and output to flatMap. See Status.

Based on flatMapSwitch, but tracks the status of input and output to flatMap. See Status.

Attributes

Inherited from:
BaseObservable
def foreach(onNext: A => Unit)(implicit owner: Owner): Subscription

Create an external observer from a function and subscribe it to this observable.

Create an external observer from a function and subscribe it to this observable.

Note: since you won't have a reference to the observer, you will need to call Subscription.kill() to unsubscribe

Attributes

Inherited from:
BaseObservable
final override def hashCode(): Int

Force reference equality checks. See comment for equals.

Force reference equality checks. See comment for equals.

Attributes

Definition Classes
Inherited from:
BaseObservable
override def map[B](project: A => B): Signal[B]

Value parameters

project

Note: guarded against exceptions

Attributes

Definition Classes
Inherited from:
Signal
def mapTo[B](value: => B): Self[B]

value is passed by name, so it will be evaluated whenever the Observable fires. Use it to sample mutable values (e.g. myInput.ref.value in Laminar).

value is passed by name, so it will be evaluated whenever the Observable fires. Use it to sample mutable values (e.g. myInput.ref.value in Laminar).

See also: mapToStrict

Value parameters

value

Note: guarded against exceptions

Attributes

Inherited from:
BaseObservable
def mapToStrict[B](value: B): Self[B]

value is evaluated strictly, only once, when this method is called.

value is evaluated strictly, only once, when this method is called.

See also: mapTo

Attributes

Inherited from:
BaseObservable
def mapToUnit: Self[Unit]

Attributes

Inherited from:
BaseObservable
def matchStreamOrSignal[B](ifStream: EventStream[A] => B, ifSignal: Signal[A] => B): B

Attributes

Inherited from:
BaseObservable
override protected def maybeWillStart(): Unit

Attributes

Definition Classes
Inherited from:
WritableObservable
override protected def numAllObservers: Int

Total number of internal and external observers

Total number of internal and external observers

Attributes

Definition Classes
Inherited from:
WritableObservable
def observe(implicit owner: Owner): OwnedSignal[A]

Add a noop observer to this signal to ensure that it's started. This lets you access .now and .tryNow on the resulting StrictSignal.

Add a noop observer to this signal to ensure that it's started. This lets you access .now and .tryNow on the resulting StrictSignal.

You can use myStream.toWeakSignal.observe.tryNow() to read the last emitted value from event streams just as well.

Attributes

Inherited from:
Signal
override def recover[B >: A](pf: PartialFunction[Throwable, Option[B]]): Signal[B]

Value parameters

pf

Note: guarded against exceptions

Attributes

Definition Classes
Inherited from:
Signal
def recoverIgnoreErrors: Self[A]

Attributes

Inherited from:
BaseObservable
override def recoverToEither: Signal[Either[Throwable, A]]

Convert this to an observable that emits Left(err) instead of erroring

Convert this to an observable that emits Left(err) instead of erroring

Attributes

Definition Classes
Inherited from:
Signal
override def recoverToTry: Signal[Try[A]]

Convert this to an observable that emits Failure(err) instead of erroring

Convert this to an observable that emits Failure(err) instead of erroring

Attributes

Definition Classes
Inherited from:
Signal
def scanLeft[B](makeInitial: A => B)(fn: (B, A) => B): Signal[B]

A signal that emits the accumulated value every time that the parent signal emits.

A signal that emits the accumulated value every time that the parent signal emits.

Value parameters

fn

Note: guarded against exceptions

makeInitial

Note: guarded against exceptions

Attributes

Inherited from:
Signal
def scanLeftRecover[B](makeInitial: Try[A] => Try[B])(fn: (Try[B], Try[A]) => Try[B]): Signal[B]

A signal that emits the accumulated value every time that the parent signal emits.

A signal that emits the accumulated value every time that the parent signal emits.

Value parameters

fn

(currentValue, nextParentValue) => nextValue

makeInitial

currentParentValue => initialValue Note: must not throw

Attributes

Inherited from:
Signal
def setDisplayName(name: String): Named.this.type

Set the display name for this instance (observable or observer).

Set the display name for this instance (observable or observer).

  • This method modifies the instance and returns this. It does not create a new instance.
  • New name you set will override the previous name, if any. This might change in the future. For the sake of sanity, don't call this more than once for the same instance.
  • If display name is set, toString will output it instead of the standard type@hashcode string

Attributes

Inherited from:
Named
def tapEach[U](f: A => U): Self[A]

Execute a side effecting callback every time the observable emits. If it's a signal, it also runs when its initial value is evaluated.

Execute a side effecting callback every time the observable emits. If it's a signal, it also runs when its initial value is evaluated.

Note: some signals such as stream.startWith or signal.composeAll have cacheInitialValue config, which could affect the number of times this callback is called in cases when you re-start a signal that was previously started, but has never emitted events before. In such cases, if cacheInitialValue == false (the default) , it will cause the signal's initial value to be re-evaluated, and this will in turn trigger the provided tapEach callback.

See com.raquo.airstream.misc.SignalFromStream

// #TODO[API] How to better type this? Note: Do not provide a callback that returns a LAZY value such as EventStream, it will not be started. I may eventually add a flatTapEach method for this.

Note: Calling tapEach on an observable does not add observers to it. The callback will only run if something else is listening to the observable.

Note: The primary method of running side effects in Airstream is putting them into Observers. In general, it's good practice to keep Observables themselves free of side effects. Airstream is actually pretty good at handling non-"pure" observables, but it's better to have such separation of concerns for your own sanity and the code's predictability / maintainability.

Note: This method is called tapEach for consistency with Scala collections. Scala also has a general tap method available by importing util.chaining.*.

Attributes

Inherited from:
BaseObservable
override def toObservable: Signal[A]

Attributes

Definition Classes
Inherited from:
Signal
def toSignalIfStream[B >: A](ifStream: EventStream[A] => Signal[B]): Signal[B]

Attributes

Inherited from:
BaseObservable
def toStreamIfSignal[B >: A](ifSignal: Signal[A] => EventStream[B]): EventStream[B]

Attributes

Inherited from:
BaseObservable
final override def toString: String

Override defaultDisplayName instead of this, if you need to.

Override defaultDisplayName instead of this, if you need to.

Attributes

Definition Classes
Named -> Any
Inherited from:
Named
def toWeakSignal: Signal[Option[A]]

Convert this observable to a signal of Option[A]. If it is a stream, set initial value to None.

Convert this observable to a signal of Option[A]. If it is a stream, set initial value to None.

Attributes

Inherited from:
BaseObservable

Deprecated and Inherited methods

def foldLeft[B](makeInitial: A => B)(fn: (B, A) => B): Signal[B]

Attributes

Deprecated
true
Inherited from:
Signal
def foldLeftRecover[B](makeInitial: Try[A] => Try[B])(fn: (Try[B], Try[A]) => Try[B]): Signal[B]

Attributes

Deprecated
true
Inherited from:
Signal

Concrete fields

protected var maybeLastSeenCurrentValue: UndefOr[Try[A]]

Inherited fields

protected val externalObservers: ObserverList[Observer[A]]

Note: Observer can be added more than once to an Observable. If so, it will observe each event as many times as it was added.

Note: Observer can be added more than once to an Observable. If so, it will observe each event as many times as it was added.

Attributes

Inherited from:
WritableObservable
protected val internalObservers: ObserverList[InternalObserver[A]]

Note: This is enforced to be a Set outside of the type system #performance

Note: This is enforced to be a Set outside of the type system #performance

Attributes

Inherited from:
WritableObservable
protected var willStartDone: Boolean

Set to true after onWillStart finishes, and until onStop finishes. It's set to false all other times. We need this to prevent onWillStart from running twice in weird cases (we have a test for that).

Set to true after onWillStart finishes, and until onStop finishes. It's set to false all other times. We need this to prevent onWillStart from running twice in weird cases (we have a test for that).

Attributes

Inherited from:
WritableObservable
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