diff --git a/src/ReplaySubject.ts b/src/ReplaySubject.ts index 4161a6cfb7..862633b392 100644 --- a/src/ReplaySubject.ts +++ b/src/ReplaySubject.ts @@ -3,7 +3,7 @@ import { IScheduler } from './Scheduler'; import { queue } from './scheduler/queue'; import { Subscriber } from './Subscriber'; import { Subscription } from './Subscription'; -import { ObserveOnSubscriber } from './operator/observeOn'; +import { ObserveOnSubscriber } from './operators/observeOn'; import { ObjectUnsubscribedError } from './util/ObjectUnsubscribedError'; import { SubjectSubscription } from './SubjectSubscription'; /** diff --git a/src/observable/FromObservable.ts b/src/observable/FromObservable.ts index f1de29590b..8970389e3b 100644 --- a/src/observable/FromObservable.ts +++ b/src/observable/FromObservable.ts @@ -10,7 +10,7 @@ import { IScheduler } from '../Scheduler'; import { iterator as Symbol_iterator } from '../symbol/iterator'; import { Observable, ObservableInput } from '../Observable'; import { Subscriber } from '../Subscriber'; -import { ObserveOnSubscriber } from '../operator/observeOn'; +import { ObserveOnSubscriber } from '../operators/observeOn'; import { observable as Symbol_observable } from '../symbol/observable'; /** diff --git a/src/operator/observeOn.ts b/src/operator/observeOn.ts index ecbacd9899..cdbef0d03f 100644 --- a/src/operator/observeOn.ts +++ b/src/operator/observeOn.ts @@ -1,11 +1,6 @@ import { Observable } from '../Observable'; import { IScheduler } from '../Scheduler'; -import { Operator } from '../Operator'; -import { PartialObserver } from '../Observer'; -import { Subscriber } from '../Subscriber'; -import { Notification } from '../Notification'; -import { TeardownLogic } from '../Subscription'; -import { Action } from '../scheduler/Action'; +import { observeOn as higherOrder } from '../operators'; /** * @@ -54,59 +49,5 @@ import { Action } from '../scheduler/Action'; * @owner Observable */ export function observeOn(this: Observable, scheduler: IScheduler, delay: number = 0): Observable { - return this.lift(new ObserveOnOperator(scheduler, delay)); -} - -export class ObserveOnOperator implements Operator { - constructor(private scheduler: IScheduler, private delay: number = 0) { - } - - call(subscriber: Subscriber, 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 extends Subscriber { - static dispatch(this: Action, arg: ObserveOnMessage) { - const { notification, destination } = arg; - notification.observe(destination); - this.unsubscribe(); - } - - constructor(destination: Subscriber, - private scheduler: IScheduler, - private delay: number = 0) { - super(destination); - } - - private scheduleMessage(notification: Notification): void { - this.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)); - } - - protected _complete(): void { - this.scheduleMessage(Notification.createComplete()); - } -} - -export class ObserveOnMessage { - constructor(public notification: Notification, - public destination: PartialObserver) { - } + return higherOrder(scheduler, delay)(this); } diff --git a/src/operators/index.ts b/src/operators/index.ts index 048a7561cc..e8be79d1a4 100644 --- a/src/operators/index.ts +++ b/src/operators/index.ts @@ -20,6 +20,7 @@ export { mergeAll } from './mergeAll'; export { mergeMap } from './mergeMap'; export { min } from './min'; export { multicast } from './multicast'; +export { observeOn } from './observeOn'; export { publish } from './publish'; export { race } from './race'; export { reduce } from './reduce'; diff --git a/src/operators/observeOn.ts b/src/operators/observeOn.ts new file mode 100644 index 0000000000..ab86f701f2 --- /dev/null +++ b/src/operators/observeOn.ts @@ -0,0 +1,115 @@ +import { Observable } from '../Observable'; +import { IScheduler } from '../Scheduler'; +import { Operator } from '../Operator'; +import { PartialObserver } from '../Observer'; +import { Subscriber } from '../Subscriber'; +import { Notification } from '../Notification'; +import { TeardownLogic } from '../Subscription'; +import { Action } from '../scheduler/Action'; +import { MonoTypeOperatorFunction } from '../interfaces'; + +/** + * + * Re-emits all notifications from source Observable with specified scheduler. + * + * Ensure a specific scheduler is used, from outside of an Observable. + * + * `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. + * 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} Observable that emits the same notifications as the source Observable, + * but with provided scheduler. + * + * @method observeOn + * @owner Observable + */ +export function observeOn(scheduler: IScheduler, delay: number = 0): MonoTypeOperatorFunction { + return function observeOnOperatorFunction(source: Observable): Observable { + return source.lift(new ObserveOnOperator(scheduler, delay)); + }; +} + +export class ObserveOnOperator implements Operator { + constructor(private scheduler: IScheduler, private delay: number = 0) { + } + + call(subscriber: Subscriber, 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 extends Subscriber { + static dispatch(this: Action, arg: ObserveOnMessage) { + const { notification, destination } = arg; + notification.observe(destination); + this.unsubscribe(); + } + + constructor(destination: Subscriber, + private scheduler: IScheduler, + private delay: number = 0) { + super(destination); + } + + private scheduleMessage(notification: Notification): void { + this.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)); + } + + protected _complete(): void { + this.scheduleMessage(Notification.createComplete()); + } +} + +export class ObserveOnMessage { + constructor(public notification: Notification, + public destination: PartialObserver) { + } +}