Skip to main content

StateObservable

Represents an Observable state. It has the following properties:

  1. It's multicast: The subscription is shared with all the subscribers.
  2. It replays the last emitted value to every new subscriber.
  3. It doesn't propagate complete.
  4. When all its subscribers unsubscribe, it cleans up everything, unsubscribing from the source and resetting the latest value.
interface StateObservable<T> extends Observable<T> {
  getRefCount: () => number
  getValue: (filter?: (value: T) => boolean) => T | StatePromise<T>
}

Inherits from rxjs' Observable.

methods​

getRefCount()​

Gets the current number of subscribers.

function getRefCount(this: StateObservable): number

Returns​

The current number of subscribers this StateObservable has.

getValue(filter)​

function getValue(
  this: StateObservable,
  filter?: (value: T) => boolean,
): T | StatePromise<T>

Arguments​

  • filter: (Optional) A function that will exclude value as a possible value returned by this function. Defaults to () => true (every value is returned)

Returns​

Either:

  • The latest value, if this StateObservable has already emitted any.
  • A promise that will resolve the first value, if this StateObservable hasn't emitted any yet.
note

  • Calling this method will throw an error if this StateObservable doesn't have any subscription active.

  • The promise returned by this method will reject if the observable completes without emitting any value, or if all subscribers unsubscribe before the observable emits something.

DefaultedStateObservable​

A StateObservable that was provided with a default value.

interface DefaultedStateObservable<T> extends StateObservable<T> {
  getDefaultValue: () => T
  getValue: (filter?: (value: T) => boolean) => T
}

Inherits from StateObservable and rxjs' Observable.

getDefaultValue()​

Gets the default value set to this DefaultedStateObservable

function getDefaultValue(this: DefaultedStateObservable<T>): T

Returns​

The default value of this DefaultedStateObservable

getValue(filter)​

function getValue(this: StateObservable, filter?: (value: T) => boolean): T

Arguments​

  • filter: (Optional) A function that will exclude value as a possible value returned by this function. Defaults to () => true (every value is returned). If the value is excluded, it will return the default value instead.

Returns​

Either:

  • The latest value, if this DefaultedStateObservable has already emitted any.
  • The default value, if this DefaultedStateObservable hasn't emitted any yet.
note

The getValue() method of DefaultedStateObservable overrides the one from StateObservable.

This means it won't return a Promise and it won't throw errors as the original StateObservable does.

See also​