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Use async pipe #227

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40 changes: 18 additions & 22 deletions recipes/smartcounter.md
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Original file line number Diff line number Diff line change
Expand Up @@ -66,45 +66,46 @@ appropriate transition.
#### Angular Version

(
[StackBlitz](https://stackblitz.com/edit/angular-gcnqlq?file=app%2Fnumber-tracker.component.ts)
[StackBlitz](https://stackblitz.com/edit/angular-27anmw?embed=1&file=app/number-tracker.component.ts)
)

```js
import { Component, Input, OnDestroy } from '@angular/core';
import { Component, Input, ChangeDetectionStrategy } from '@angular/core';
import { Subject } from 'rxjs/Subject';
import { timer } from 'rxjs/observable/timer';
import { switchMap, startWith, scan, takeWhile, takeUntil, mapTo } from 'rxjs/operators';
import { of } from 'rxjs/observable/of';
import { Observable } from 'rxjs';
import { switchMap, startWith, scan, takeWhile, mapTo, withLatestFrom } from 'rxjs/operators';

@Component({
selector: 'number-tracker',
template: `
<h3> {{ currentNumber }}</h3>
`
<h3> {{ (currentNumber$ | async) || 0 }}</h3>
`,
changeDetection: ChangeDetectionStrategy.OnPush
})
export class NumberTrackerComponent implements OnDestroy {
export class NumberTrackerComponent {
@Input()
set end(endRange: number) {
this._counterSub$.next(endRange);
}
@Input() countInterval = 20;
public currentNumber = 0;
public currentNumber$ = of(0);
private _counterSub$ = new Subject();
private _onDestroy$ = new Subject();

constructor() {
this._counterSub$
this.currentNumber$ = this._counterSub$
.pipe(
switchMap(endRange => {
withLatestFrom(this.currentNumber$),
switchMap(([endRange, currentNumber]) => {
return timer(0, this.countInterval).pipe(
mapTo(this.positiveOrNegative(endRange, this.currentNumber)),
startWith(this.currentNumber),
mapTo(this.positiveOrNegative(endRange, currentNumber)),
startWith(currentNumber),
scan((acc: number, curr: number) => acc + curr),
takeWhile(this.isApproachingRange(endRange, this.currentNumber))
takeWhile(this.isApproachingRange(endRange, currentNumber))
)
}),
takeUntil(this._onDestroy$)
)
.subscribe((val: number) => this.currentNumber = val);
})
);
}

private positiveOrNegative(endRange, currentNumber) {
Expand All @@ -116,11 +117,6 @@ export class NumberTrackerComponent implements OnDestroy {
? val => val <= endRange
: val => val >= endRange;
}

ngOnDestroy() {
this._onDestroy$.next();
this._onDestroy$.complete();
}
}
```

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