| import { multicast as higherOrder } from '../operators/multicast'; |
| /* tslint:enable:max-line-length */ |
| /** |
| * Allows source Observable to be subscribed only once with a Subject of choice, |
| * while still sharing its values between multiple subscribers. |
| * |
| * <span class="informal">Subscribe to Observable once, but send its values to multiple subscribers.</span> |
| * |
| * <img src="./img/multicast.png" width="100%"> |
| * |
| * `multicast` is an operator that works in two modes. |
| * |
| * In the first mode you provide a single argument to it, which can be either an initialized Subject or a Subject |
| * factory. As a result you will get a special kind of an Observable - a {@link ConnectableObservable}. It can be |
| * subscribed multiple times, just as regular Observable, but it won't subscribe to the source Observable at that |
| * moment. It will do it only if you call its `connect` method. This means you can essentially control by hand, when |
| * source Observable will be actually subscribed. What is more, ConnectableObservable will share this one subscription |
| * between all of its subscribers. This means that, for example, `ajax` Observable will only send a request once, |
| * even though usually it would send a request per every subscriber. Since it sends a request at the moment of |
| * subscription, here request would be sent when the `connect` method of a ConnectableObservable is called. |
| * |
| * The most common pattern of using ConnectableObservable is calling `connect` when the first consumer subscribes, |
| * keeping the subscription alive while several consumers come and go and finally unsubscribing from the source |
| * Observable, when the last consumer unsubscribes. To not implement that logic over and over again, |
| * ConnectableObservable has a special operator, `refCount`. When called, it returns an Observable, which will count |
| * the number of consumers subscribed to it and keep ConnectableObservable connected as long as there is at least |
| * one consumer. So if you don't actually need to decide yourself when to connect and disconnect a |
| * ConnectableObservable, use `refCount`. |
| * |
| * The second mode is invoked by calling `multicast` with an additional, second argument - selector function. |
| * This function accepts an Observable - which basically mirrors the source Observable - and returns Observable |
| * as well, which should be the input stream modified by any operators you want. Note that in this |
| * mode you cannot provide initialized Subject as a first argument - it has to be a Subject factory. If |
| * you provide selector function, `multicast` returns just a regular Observable, instead of ConnectableObservable. |
| * Thus, as usual, each subscription to this stream triggers subscription to the source Observable. However, |
| * if inside the selector function you subscribe to the input Observable multiple times, actual source stream |
| * will be subscribed only once. So if you have a chain of operators that use some Observable many times, |
| * but you want to subscribe to that Observable only once, this is the mode you would use. |
| * |
| * Subject provided as a first parameter of `multicast` is used as a proxy for the single subscription to the |
| * source Observable. It means that all values from the source stream go through that Subject. Thus, if a Subject |
| * has some special properties, Observable returned by `multicast` will have them as well. If you want to use |
| * `multicast` with a Subject that is one of the ones included in RxJS by default - {@link Subject}, |
| * {@link AsyncSubject}, {@link BehaviorSubject}, or {@link ReplaySubject} - simply use {@link publish}, |
| * {@link publishLast}, {@link publishBehavior} or {@link publishReplay} respectively. These are actually |
| * just wrappers around `multicast`, with a specific Subject hardcoded inside. |
| * |
| * Also, if you use {@link publish} or {@link publishReplay} with a ConnectableObservables `refCount` operator, |
| * you can simply use {@link share} and {@link shareReplay} respectively, which chain these two. |
| * |
| * @example <caption>Use ConnectableObservable</caption> |
| * const seconds = Rx.Observable.interval(1000); |
| * const connectableSeconds = seconds.multicast(new Subject()); |
| * |
| * connectableSeconds.subscribe(value => console.log('first: ' + value)); |
| * connectableSeconds.subscribe(value => console.log('second: ' + value)); |
| * |
| * // At this point still nothing happens, even though we subscribed twice. |
| * |
| * connectableSeconds.connect(); |
| * |
| * // From now on `seconds` are being logged to the console, |
| * // twice per every second. `seconds` Observable was however only subscribed once, |
| * // so under the hood Observable.interval had only one clock started. |
| * |
| * @example <caption>Use selector</caption> |
| * const seconds = Rx.Observable.interval(1000); |
| * |
| * seconds |
| * .multicast( |
| * () => new Subject(), |
| * seconds => seconds.zip(seconds) // Usually zip would subscribe to `seconds` twice. |
| * // Because we are inside selector, `seconds` is subscribed once, |
| * ) // thus starting only one clock used internally by Observable.interval. |
| * .subscribe(); |
| * |
| * @see {@link publish} |
| * @see {@link publishLast} |
| * @see {@link publishBehavior} |
| * @see {@link publishReplay} |
| * @see {@link share} |
| * @see {@link shareReplay} |
| * |
| * @param {Function|Subject} subjectOrSubjectFactory - Factory function to create an intermediate Subject through |
| * which the source sequence's elements will be multicast to the selector function input Observable or |
| * ConnectableObservable returned by the operator. |
| * @param {Function} [selector] - Optional selector function that can use the input stream |
| * as many times as needed, without causing multiple subscriptions to the source stream. |
| * Subscribers to the input source will receive all notifications of the source from the |
| * time of the subscription forward. |
| * @return {Observable<T>|ConnectableObservable<T>} An Observable that emits the results of invoking the selector |
| * on the source stream or a special {@link ConnectableObservable}, if selector was not provided. |
| * |
| * @method multicast |
| * @owner Observable |
| */ |
| export function multicast(subjectOrSubjectFactory, selector) { |
| return higherOrder(subjectOrSubjectFactory, selector)(this); |
| } |
| //# sourceMappingURL=multicast.js.map |