| import { Observable } from '../Observable'; |
| import { Operator } from '../Operator'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| import { Notification } from '../Notification'; |
| import { MonoTypeOperatorFunction, PartialObserver, SchedulerAction, SchedulerLike, TeardownLogic } from '../types'; |
| |
| /** |
| * |
| * Re-emits all notifications from source Observable with specified scheduler. |
| * |
| * <span class="informal">Ensure a specific scheduler is used, from outside of an Observable.</span> |
| * |
| * `observeOn` is an operator that accepts a scheduler as a first parameter, which will be used to reschedule |
| * notifications emitted by the source Observable. It might be useful, if you do not have control over |
| * internal scheduler of a given Observable, but want to control when its values are emitted nevertheless. |
| * |
| * Returned Observable emits the same notifications (nexted values, complete and error events) as the source Observable, |
| * but rescheduled with provided scheduler. Note that this doesn't mean that source Observables internal |
| * scheduler will be replaced in any way. Original scheduler still will be used, but when the source Observable emits |
| * notification, it will be immediately scheduled again - this time with scheduler passed to `observeOn`. |
| * An anti-pattern would be calling `observeOn` on Observable that emits lots of values synchronously, to split |
| * that emissions into asynchronous chunks. For this to happen, scheduler would have to be passed into the source |
| * Observable directly (usually into the operator that creates it). `observeOn` simply delays notifications a |
| * little bit more, to ensure that they are emitted at expected moments. |
| * |
| * As a matter of fact, `observeOn` accepts second parameter, which specifies in milliseconds with what delay notifications |
| * will be emitted. The main difference between {@link delay} operator and `observeOn` is that `observeOn` |
| * will delay all notifications - including error notifications - while `delay` will pass through error |
| * from source Observable immediately when it is emitted. In general it is highly recommended to use `delay` operator |
| * for any kind of delaying of values in the stream, while using `observeOn` to specify which scheduler should be used |
| * for notification emissions in general. |
| * |
| * ## Example |
| * Ensure values in subscribe are called just before browser repaint. |
| * ```ts |
| * import { interval } from 'rxjs'; |
| * import { observeOn } from 'rxjs/operators'; |
| * |
| * const intervals = interval(10); // Intervals are scheduled |
| * // with async scheduler by default... |
| * intervals.pipe( |
| * observeOn(animationFrameScheduler), // ...but we will observe on animationFrame |
| * ) // scheduler to ensure smooth animation. |
| * .subscribe(val => { |
| * someDiv.style.height = val + 'px'; |
| * }); |
| * ``` |
| * |
| * @see {@link delay} |
| * |
| * @param {SchedulerLike} scheduler Scheduler that will be used to reschedule notifications from source Observable. |
| * @param {number} [delay] Number of milliseconds that states with what delay every notification should be rescheduled. |
| * @return {Observable<T>} Observable that emits the same notifications as the source Observable, |
| * but with provided scheduler. |
| * |
| * @method observeOn |
| * @owner Observable |
| */ |
| export function observeOn<T>(scheduler: SchedulerLike, delay: number = 0): MonoTypeOperatorFunction<T> { |
| return function observeOnOperatorFunction(source: Observable<T>): Observable<T> { |
| return source.lift(new ObserveOnOperator(scheduler, delay)); |
| }; |
| } |
| |
| export class ObserveOnOperator<T> implements Operator<T, T> { |
| constructor(private scheduler: SchedulerLike, private delay: number = 0) { |
| } |
| |
| call(subscriber: Subscriber<T>, source: any): TeardownLogic { |
| return source.subscribe(new ObserveOnSubscriber(subscriber, this.scheduler, this.delay)); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| export class ObserveOnSubscriber<T> extends Subscriber<T> { |
| /** @nocollapse */ |
| static dispatch(this: SchedulerAction<ObserveOnMessage>, arg: ObserveOnMessage) { |
| const { notification, destination } = arg; |
| notification.observe(destination); |
| this.unsubscribe(); |
| } |
| |
| constructor(destination: Subscriber<T>, |
| private scheduler: SchedulerLike, |
| private delay: number = 0) { |
| super(destination); |
| } |
| |
| private scheduleMessage(notification: Notification<any>): void { |
| const destination = this.destination as Subscription; |
| destination.add(this.scheduler.schedule( |
| ObserveOnSubscriber.dispatch, |
| this.delay, |
| new ObserveOnMessage(notification, this.destination) |
| )); |
| } |
| |
| protected _next(value: T): void { |
| this.scheduleMessage(Notification.createNext(value)); |
| } |
| |
| protected _error(err: any): void { |
| this.scheduleMessage(Notification.createError(err)); |
| this.unsubscribe(); |
| } |
| |
| protected _complete(): void { |
| this.scheduleMessage(Notification.createComplete()); |
| this.unsubscribe(); |
| } |
| } |
| |
| export class ObserveOnMessage { |
| constructor(public notification: Notification<any>, |
| public destination: PartialObserver<any>) { |
| } |
| } |