50 lines
3.1 KiB
TypeScript
50 lines
3.1 KiB
TypeScript
import { Observable } from '../Observable';
|
|
import { IScheduler } from '../Scheduler';
|
|
/**
|
|
*
|
|
* 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 <caption>Ensure values in subscribe are called just before browser repaint.</caption>
|
|
* const intervals = Rx.Observable.interval(10); // Intervals are scheduled
|
|
* // with async scheduler by default...
|
|
*
|
|
* intervals
|
|
* .observeOn(Rx.Scheduler.animationFrame) // ...but we will observe on animationFrame
|
|
* .subscribe(val => { // scheduler to ensure smooth animation.
|
|
* someDiv.style.height = val + 'px';
|
|
* });
|
|
*
|
|
* @see {@link delay}
|
|
*
|
|
* @param {IScheduler} 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 declare function observeOn<T>(this: Observable<T>, scheduler: IScheduler, delay?: number): Observable<T>;
|