Interface Signal<T>

Base signal interface with read-only access to the signal value. It is subscribable and must emit the current value directly on subscription.

interface Signal<T = unknown> {
    get(): T;
    getVersion(): unknown;
    isValid(): boolean;
    isWatched(): boolean;
    subscribe(observer: Observer<T> | (next: T) => void): Unsubscribable;
    validate(): void;
}

Type Parameters

  • T = unknown

Hierarchy (View Summary)

Methods

get getVersion isValid isWatched subscribe validate

Methods

get

getVersion

  • getVersion(): unknown

  • Returns the current signal value version. This value is used to determine if a dependency has changed. The most simple implementation would be a number which is incremented every time the signal value really has changed. The version type doesn't matter but must be comparable with ===.

    Returns unknown

    The current signal value version.

isValid

  • isValid(): boolean

  • Checks if signal value is still valid. When signal has no dependencies then this method can always return true. If signal has dependencies then it must check if any dependency has changed or became invalid. If yes, then this method must return false and the signal will be re-validated by calling (). If all dependency are valid/unchanged then this method must return true to indicate that the signal value is still valid.

    Returns boolean

    True if signal value is valid, false if it must be re-validated.

isWatched

  • isWatched(): boolean

  • Returns boolean

    True if signal is watched (has subscribed observers) or false if not.

subscribe

  • subscribe(observer: Observer<T> | (next: T) => void): Unsubscribable

  • Subscribes the given observer to this object.

    Parameters

    • observer: Observer<T> | (next: T) => void

      The observer to subscribe.

    Returns Unsubscribable

    Object which can be used to unsubscribe the observer.

validate

  • validate(): void

  • Called when () returned false and the current value of this signal is needed. Must compute/fetch and cache the new value so the next call to () returns a valid value. When signal has no dependencies and () is implemented to always return true then this method can stay empty as it has nothing to validate/update.

    Returns void

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