es6/util/subscribeToResult.js

import { root } from './root';
import { isArrayLike } from './isArrayLike';
import { isPromise } from './isPromise';
import { isObject } from './isObject';
import { Observable } from '../Observable';
import { iterator as Symbol_iterator } from '../symbol/iterator';
import { InnerSubscriber } from '../InnerSubscriber';
import { observable as Symbol_observable } from '../symbol/observable';
export function subscribeToResult(outerSubscriber, result, outerValue, outerIndex) {
    let destination = new InnerSubscriber(outerSubscriber, outerValue, outerIndex);
    if (destination.closed) {
        return null;
    }
    if (result instanceof Observable) {
        if (result._isScalar) {
            destination.next(result.value);
            destination.complete();
            return null;
        }
        else {
            destination.syncErrorThrowable = true;
            return result.subscribe(destination);
        }
    }
    else if (isArrayLike(result)) {
        for (let i = 0, len = result.length; i < len && !destination.closed; i++) {
            destination.next(result[i]);
        }
        if (!destination.closed) {
            destination.complete();
        }
    }
    else if (isPromise(result)) {
        result.then((value) => {
            if (!destination.closed) {
                destination.next(value);
                destination.complete();
            }
        }, (err) => destination.error(err))
            .then(null, (err) => {
            // Escaping the Promise trap: globally throw unhandled errors
            root.setTimeout(() => { throw err; });
        });
        return destination;
    }
    else if (result && typeof result[Symbol_iterator] === 'function') {
        const iterator = result[Symbol_iterator]();
        do {
            let item = iterator.next();
            if (item.done) {
                destination.complete();
                break;
            }
            destination.next(item.value);
            if (destination.closed) {
                break;
            }
        } while (true);
    }
    else if (result && typeof result[Symbol_observable] === 'function') {
        const obs = result[Symbol_observable]();
        if (typeof obs.subscribe !== 'function') {
            destination.error(new TypeError('Provided object does not correctly implement Symbol.observable'));
        }
        else {
            return obs.subscribe(new InnerSubscriber(outerSubscriber, outerValue, outerIndex));
        }
    }
    else {
        const value = isObject(result) ? 'an invalid object' : `'${result}'`;
        const msg = `You provided ${value} where a stream was expected.`
            + ' You can provide an Observable, Promise, Array, or Iterable.';
        destination.error(new TypeError(msg));
    }
    return null;
}
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