es6/observable/FromObservable.js

import { isArray } from '../util/isArray';
import { isArrayLike } from '../util/isArrayLike';
import { isPromise } from '../util/isPromise';
import { PromiseObservable } from './PromiseObservable';
import { IteratorObservable } from './IteratorObservable';
import { ArrayObservable } from './ArrayObservable';
import { ArrayLikeObservable } from './ArrayLikeObservable';
import { iterator as Symbol_iterator } from '../symbol/iterator';
import { Observable } from '../Observable';
import { ObserveOnSubscriber } from '../operator/observeOn';
import { observable as Symbol_observable } from '../symbol/observable';
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @extends {Ignored}
 * @hide true
 */
export class FromObservable extends Observable {
    constructor(ish, scheduler) {
        super(null);
        this.ish = ish;
        this.scheduler = scheduler;
    }
    /**
     * 从一个数组、类数组对象、Promise、迭代器对象或者类 Observable 对象创建一个 Observable.
     *
     * <span class="informal">几乎可以把任何东西都能转化为Observable.</span>
     *
     * <img src="./img/from.png" width="100%">
     *
     * 将各种其他对象和数据类型转化为 Observables。 `from`将 Promise、类数组对象、迭代器对象
     * (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable)
     * 转化为 Observable ，该 Observable 发出 promise、数组或者迭代器的成员。 字符串，在这种上下文里，会被当做字符数组。
     * 类 Observable 对象(包括ES2015里的 Observable 方法)也可以通过此操作符进行转换。
     *
     * @example <caption>将数组转化为 Observable</caption>
     * var array = [10, 20, 30];
     * var result = Rx.Observable.from(array);
     * result.subscribe(x => console.log(x));
     *
     * // 结果如下:
     * // 10 20 30
     *
     * @example <caption>将一个无限的迭代器(来自于 generator)转化为 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 一个可以被订阅的对象, Promise, 类
     * Observable, 数组, 迭代器或者类数组对象可以被转化。
     * @param {Scheduler} [scheduler] 调度器，用来调度值的发送。
     * @return {Observable<T>} Observable的值来自于输入对象的转化。
     * @static true
     * @name from
     * @owner Observable
     */
    static create(ish, scheduler) {
        if (ish != null) {
            if (typeof ish[Symbol_observable] === 'function') {
                if (ish instanceof Observable && !scheduler) {
                    return ish;
                }
                return new FromObservable(ish, scheduler);
            }
            else if (isArray(ish)) {
                return new ArrayObservable(ish, scheduler);
            }
            else if (isPromise(ish)) {
                return new PromiseObservable(ish, scheduler);
            }
            else if (typeof ish[Symbol_iterator] === 'function' || typeof ish === 'string') {
                return new IteratorObservable(ish, scheduler);
            }
            else if (isArrayLike(ish)) {
                return new ArrayLikeObservable(ish, scheduler);
            }
        }
        throw new TypeError((ish !== null && typeof ish || ish) + ' is not observable');
    }
    _subscribe(subscriber) {
        const ish = this.ish;
        const scheduler = this.scheduler;
        if (scheduler == null) {
            return ish[Symbol_observable]().subscribe(subscriber);
        }
        else {
            return ish[Symbol_observable]().subscribe(new ObserveOnSubscriber(subscriber, scheduler, 0));
        }
    }
}
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