es6/Notification.js

import { Observable } from './Observable';
/**
 * Represents a push-based event or value that an {@link Observable} can emit.
 * This class is particularly useful for operators that manage notifications,
 * like {@link materialize}, {@link dematerialize}, {@link observeOn}, and
 * others. Besides wrapping the actual delivered value, it also annotates it
 * with metadata of, for instance, what type of push message it is (`next`,
 * `error`, or `complete`).
 *
 * @see {@link materialize}
 * @see {@link dematerialize}
 * @see {@link observeOn}
 *
 * @class Notification<T>
 */
export class Notification {
    constructor(kind, value, error) {
        this.kind = kind;
        this.value = value;
        this.error = error;
        this.hasValue = kind === 'N';
    }
    /**
     * Delivers to the given `observer` the value wrapped by this Notification.
     * @param {Observer} observer
     * @return
     */
    observe(observer) {
        switch (this.kind) {
            case 'N':
                return observer.next && observer.next(this.value);
            case 'E':
                return observer.error && observer.error(this.error);
            case 'C':
                return observer.complete && observer.complete();
        }
    }
    /**
     * Given some {@link Observer} callbacks, deliver the value represented by the
     * current Notification to the correctly corresponding callback.
     * @param {function(value: T): void} next An Observer `next` callback.
     * @param {function(err: any): void} [error] An Observer `error` callback.
     * @param {function(): void} [complete] An Observer `complete` callback.
     * @return {any}
     */
    do(next, error, complete) {
        const kind = this.kind;
        switch (kind) {
            case 'N':
                return next && next(this.value);
            case 'E':
                return error && error(this.error);
            case 'C':
                return complete && complete();
        }
    }
    /**
     * Takes an Observer or its individual callback functions, and calls `observe`
     * or `do` methods accordingly.
     * @param {Observer|function(value: T): void} nextOrObserver An Observer or
     * the `next` callback.
     * @param {function(err: any): void} [error] An Observer `error` callback.
     * @param {function(): void} [complete] An Observer `complete` callback.
     * @return {any}
     */
    accept(nextOrObserver, error, complete) {
        if (nextOrObserver && typeof nextOrObserver.next === 'function') {
            return this.observe(nextOrObserver);
        }
        else {
            return this.do(nextOrObserver, error, complete);
        }
    }
    /**
     * Returns a simple Observable that just delivers the notification represented
     * by this Notification instance.
     * @return {any}
     */
    toObservable() {
        const kind = this.kind;
        switch (kind) {
            case 'N':
                return Observable.of(this.value);
            case 'E':
                return Observable.throw(this.error);
            case 'C':
                return Observable.empty();
        }
        throw new Error('unexpected notification kind value');
    }
    /**
     * A shortcut to create a Notification instance of the type `next` from a
     * given value.
     * @param {T} value The `next` value.
     * @return {Notification<T>} The "next" Notification representing the
     * argument.
     */
    static createNext(value) {
        if (typeof value !== 'undefined') {
            return new Notification('N', value);
        }
        return Notification.undefinedValueNotification;
    }
    /**
     * A shortcut to create a Notification instance of the type `error` from a
     * given error.
     * @param {any} [err] The `error` error.
     * @return {Notification<T>} The "error" Notification representing the
     * argument.
     */
    static createError(err) {
        return new Notification('E', undefined, err);
    }
    /**
     * A shortcut to create a Notification instance of the type `complete`.
     * @return {Notification<any>} The valueless "complete" Notification.
     */
    static createComplete() {
        return Notification.completeNotification;
    }
}
Notification.completeNotification = new Notification('C');
Notification.undefinedValueNotification = new Notification('N', undefined);
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