work.suroh.tk/node_modules/rxjs/_esm2015/Notification.js

124 lines
4.3 KiB
JavaScript

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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