FromObservable.ts
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import { isArray } from '../util/isArray';
import { isPromise } from '../util/isPromise';
import { PromiseObservable } from './PromiseObservable';
import { IteratorObservable } from'./IteratorObservable';
import { ArrayObservable } from './ArrayObservable';
import { ArrayLikeObservable } from './ArrayLikeObservable';
import { Scheduler } from '../Scheduler';
import { $$iterator } from '../symbol/iterator';
import { Observable, ObservableInput } from '../Observable';
import { Subscriber } from '../Subscriber';
import { ObserveOnSubscriber } from '../operator/observeOn';
import { $$observable } from '../symbol/observable';
const isArrayLike = (<T>(x: any): x is ArrayLike<T> => x && typeof x.length === 'number');
/**
* We need this JSDoc comment for affecting ESDoc.
* @extends {Ignored}
* @hide true
*/
export class FromObservable<T> extends Observable<T> {
constructor(private ish: ObservableInput<T>, private scheduler?: Scheduler) {
super(null);
}
static create<T>(ish: ObservableInput<T>, scheduler?: Scheduler): Observable<T>;
static create<T, R>(ish: ArrayLike<T>, scheduler?: Scheduler): Observable<R>;
/**
* Creates an Observable from an Array, an array-like object, a Promise, an
* iterable object, or an Observable-like object.
*
* <span class="informal">Converts almost anything to an Observable.</span>
*
* <img src="./img/from.png" width="100%">
*
* Convert various other objects and data types into Observables. `from`
* converts a Promise or an array-like or an
* [iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable)
* object into an Observable that emits the items in that promise or array or
* iterable. A String, in this context, is treated as an array of characters.
* Observable-like objects (contains a function named with the ES2015 Symbol
* for Observable) can also be converted through this operator.
*
* @example <caption>Converts an array to an Observable</caption>
* var array = [10, 20, 30];
* var result = Rx.Observable.from(array);
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // 10 20 30
*
* @example <caption>Convert an infinite iterable (from a generator) to an Observable</caption>
* function* generateDoubles(seed) {
* var i = seed;
* while (true) {
* yield i;
* i = 2 * i; // double it
* }
* }
*
* var iterator = generateDoubles(3);
* var result = Rx.Observable.from(iterator).take(10);
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // 3 6 12 24 48 96 192 384 768 1536
*
* @see {@link create}
* @see {@link fromEvent}
* @see {@link fromEventPattern}
* @see {@link fromPromise}
*
* @param {ObservableInput<T>} ish A subscribable object, a Promise, an
* Observable-like, an Array, an iterable or an array-like object to be
* converted.
* @param {Scheduler} [scheduler] The scheduler on which to schedule the
* emissions of values.
* @return {Observable<T>} The Observable whose values are originally from the
* input object that was converted.
* @static true
* @name from
* @owner Observable
*/
static create<T>(ish: ObservableInput<T>, scheduler?: Scheduler): Observable<T> {
if (ish != null) {
if (typeof ish[$$observable] === 'function') {
if (ish instanceof Observable && !scheduler) {
return ish;
}
return new FromObservable<T>(ish, scheduler);
} else if (isArray(ish)) {
return new ArrayObservable<T>(ish, scheduler);
} else if (isPromise(ish)) {
return new PromiseObservable<T>(ish, scheduler);
} else if (typeof ish[$$iterator] === 'function' || typeof ish === 'string') {
return new IteratorObservable<T>(ish, scheduler);
} else if (isArrayLike(ish)) {
return new ArrayLikeObservable(ish, scheduler);
}
}
throw new TypeError((ish !== null && typeof ish || ish) + ' is not observable');
}
protected _subscribe(subscriber: Subscriber<T>) {
const ish = this.ish;
const scheduler = this.scheduler;
if (scheduler == null) {
return ish[$$observable]().subscribe(subscriber);
} else {
return ish[$$observable]().subscribe(new ObserveOnSubscriber(subscriber, scheduler, 0));
}
}
}