Class AsyncObservable<Value>

An observable that can handle promises and updates listeners for each stage in the promise lifecycle. It also stores the last resolved value.

Type Parameters

  • Value

Hierarchy (View Summary)

Constructors

constructor

Properties

equalityCheck lastResolvedValue lastSetId lastSetPromise listenerMap value waitingForValueDeferredPromise

Methods

destroy dispatch getListenerCount listen listenToEvent rejectValue removeAllListeners removeListener resolveValue setPromise setValue

Constructors

constructor

  • new AsyncObservable<Value>(
        init?: Readonly<
            Partial<
                {
                    defaultValue: | Exclude<Awaited<Value>, typeof noUpdate>
                    | Promise<Exclude<Awaited<Value>, typeof noUpdate>>;
                    equalityCheck:
                        | undefined
                        | EqualityCheck<
                            {
                                [KeyType in string
                                | number
                                | symbol]: Exclude<Awaited<Value>, typeof noUpdate>[KeyType]
                            },
                        >;
                },
            >,
        >,
    ): AsyncObservable<Value>

    Type Parameters

    • Value

    Parameters

    • init: Readonly<
          Partial<
              {
                  defaultValue: | Exclude<Awaited<Value>, typeof noUpdate>
                  | Promise<Exclude<Awaited<Value>, typeof noUpdate>>;
                  equalityCheck:
                      | undefined
                      | EqualityCheck<
                          {
                              [KeyType in string
                              | number
                              | symbol]: Exclude<Awaited<Value>, typeof noUpdate>[KeyType]
                          },
                      >;
              },
          >,
      > = {}

    Returns AsyncObservable<Value>

Properties

equalityCheck

equalityCheck: EqualityCheck<
    {
        [KeyType in string
        | number
        | symbol]: Exclude<Awaited<Value>, typeof noUpdate>[KeyType]
    },
>

The function used to check equality between different values. This can be manually set at any time to change the function used.

ReadonlylastResolvedValue

lastResolvedValue: undefined | Exclude<Awaited<Value>, typeof noUpdate> = undefined

The last resolved value. This only changes when value is set to a resolved value or when a promise value resolves.

Do not set this directly. Use AsyncObservable.setValue instead.

ProtectedlastSetId

lastSetId: string = ...

Used to prevent setting different values from racing with each other.

ProtectedlastSetPromise

lastSetPromise: undefined | Promise<AllowNoUpdate<Value>>

Protected ReadonlylistenerMap

listenerMap: WeakMap<
    ObservableListener<any>,
    TypedEventListenerWithRemoval<ObservableValueUpdateEvent>,
> = ...

This is necessary so we can fire listeners that listen directly to the value, not the emitted event.

Readonlyvalue

value: AsyncValue<Value> = ...

The value which this observable currently contains. In this AsyncObservable, value may be a promise, a resolved value, or an error.

Do not set this directly. Use AsyncObservable.setValue instead.

ProtectedwaitingForValueDeferredPromise

waitingForValueDeferredPromise: DeferredPromise<
    Exclude<Awaited<Value>, typeof noUpdate>,
> = ...

Methods

destroy

Protecteddispatch

getListenerCount

listen

  • listen(
        fireImmediately: boolean,
        callback: ObservableListener<Value>,
    ): RemoveListenerCallback

    Listen to changes in the observable's value.

    Parameters

    • fireImmediately: boolean

      If true, the callback will immediately be fired with whatever the current value is.

    • callback: ObservableListener<Value>

      The callback to fire when a new value is set on the observable.

    Returns RemoveListenerCallback

    A callback to remove the listener.

listenToEvent

  • listenToEvent<
        const EventDefinition extends
            Readonly<
                {
                    type: | "observable-value-update"
                    | "observable-value-resolve"
                    | "observable-value-error"
                    | "observable-destroy"
                    | "observable-callback-call"
                    | "observable-params-update"
                    | "observable-interval-run"
                    | "observable-interval-skip"
                    | "observable-interval-rate-limited";
                },
            >,
    >(
        eventDefinition: EventDefinition,
        listenerCallback: TypedEventListenerWithRemoval<
            ExtractEventByType<ObservableEvents, EventDefinition["type"]>,
        >,
        options?: PartialWithUndefined<{}>,
    ): RemoveListenerCallback

    Listen to any event omitted by the observable rather than just the value changing.

    Type Parameters

    • const EventDefinition extends Readonly<
          {
              type: | "observable-value-update"
              | "observable-value-resolve"
              | "observable-value-error"
              | "observable-destroy"
              | "observable-callback-call"
              | "observable-params-update"
              | "observable-interval-run"
              | "observable-interval-skip"
              | "observable-interval-rate-limited";
          },
      >

    Parameters

    Returns RemoveListenerCallback

    A callback to remove the listener.

ProtectedrejectValue

  • rejectValue(error: Error): void

    Internally updates the current value when a promise value has been rejected or an error value is given.

    Parameters

    • error: Error

    Returns void

removeAllListeners

removeListener

ProtectedresolveValue

ProtectedsetPromise

setValue

  • setValue(
        value: AllowNoUpdate<Error | MaybePromise<AllowNoUpdate<Value>>>,
    ): boolean

    Set a new value to the observable. If a promise is used, value will be set to the promise and value will be automatically overridden with the resolution or rejection result of the promise once it's available.

    New resolved values will only be set and listeners will only be fired if it is not equal to the current value (as determined by equalityCheck).

    Parameters

    Returns boolean

    true if the new value was set, false otherwise.

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