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