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cleanup(cdk-scrollable): use fromEvent under the hood #12589

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Merged
merged 1 commit into from
Aug 13, 2018
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cleanup(cdk-scrollable): use fromEvent under the hood #12589

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29 changes: 13 additions & 16 deletions src/cdk/scrolling/scrollable.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,9 @@
* found in the LICENSE file at https://angular.io/license
*/

import {Directive, ElementRef, OnInit, OnDestroy, NgZone} from '@angular/core';
import {Observable, Subject} from 'rxjs';
import {Directive, ElementRef, NgZone, OnDestroy, OnInit} from '@angular/core';
import {fromEvent, Observable, Subject} from 'rxjs';
import {takeUntil} from 'rxjs/operators';
import {ScrollDispatcher} from './scroll-dispatcher';


Expand All @@ -20,36 +21,32 @@ import {ScrollDispatcher} from './scroll-dispatcher';
selector: '[cdk-scrollable], [cdkScrollable]'
})
export class CdkScrollable implements OnInit, OnDestroy {
private _elementScrolled: Subject<Event> = new Subject();
private _scrollListener = (event: Event) => this._elementScrolled.next(event);
private _destroyed = new Subject();

private _elementScrolled: Observable<Event> = Observable.create(observer =>
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Why do you need the Observable.create here? You can just do this:

private _elementScrolled = this._ngZone.runOutsideAngular(() => {
  return fromEvent(...).pipe(takeUntil(this._destroyed), tap(() => ...));
});

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What does the tap(() => ...) do here?

I was under the impression that the call to subscribe has to occur inside the runOutsideAngular function, that's why I did it this way

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Sorry, I forgot that about having to subscribe.

this._ngZone.runOutsideAngular(() =>
fromEvent(this._elementRef.nativeElement, 'scroll').pipe(takeUntil(this._destroyed))
.subscribe(observer)));

constructor(private _elementRef: ElementRef,
private _scroll: ScrollDispatcher,
private _ngZone: NgZone) {}

ngOnInit() {
this._ngZone.runOutsideAngular(() => {
this.getElementRef().nativeElement.addEventListener('scroll', this._scrollListener);
});

this._scroll.register(this);
}

ngOnDestroy() {
this._scroll.deregister(this);

if (this._scrollListener) {
this.getElementRef().nativeElement.removeEventListener('scroll', this._scrollListener);
}

this._elementScrolled.complete();
this._destroyed.next();
this._destroyed.complete();
}

/**
* Returns observable that emits when a scroll event is fired on the host element.
*/
elementScrolled(): Observable<any> {
return this._elementScrolled.asObservable();
elementScrolled(): Observable<Event> {
return this._elementScrolled;
}

getElementRef(): ElementRef {
Expand Down