How to call a service call in each 2 minutes in angular4 observable

Question

In service

this._ProductUrl =".../api/products" getProduct(): Observable <IProduct[]>{ return this._http.get(this._ProductUrl) .map((response:Response) => <IProduct[]> response.json()) .catch(this.handleError); }

app.component.ts

with interval not working

Observable .interval(2*60*1000) .timeInterval() .flatMap((this._productService.getProduct()) .subscribe((response) => { }),(err)=> {this.errorMsg =<any>err};

while hover over the line some error displays. Error in this line:

 Argument of type '(err: TimeInterval<number>) => void' is not assignable to parameter of type '(value: TimeInterval<number>, index: number) => ObservableInput<{}>'. Type 'void' is not assignable to type 'ObservableInput<{}>'

when tried like this

 Observable .interval(2*60*1000) .timeInterval() .flatMap((this._productService.getProduct(response))).subscribe((response) => { }),(err)=> {this.errorMsg =<any>err};

Error on this line:

.flatMap((this._productService.getProduct(response) [ts] Expected 0 arguments, but got 1. (property) AppComponent._productService: ProductServic

e

without Interval working fine

 this._productService.getProduct().subscribe((response) => { console.log(error); }),(err)=> {this.errorMsg =<any>err};

There is some syntax issue with above codes, please provide better solution be appreciated

Chandru · Accepted Answer · 2017-11-28 09:33:06Z

try like this :

Observable.interval(2000).subscribe((x) => { this._productService.getProduct() .subscribe((response) => { console.log('response', response) }) })

OR using flatMap() you can try like this below

Observable.interval(2000) .timeInterval() .flatMap((x) => { return this._productService.getProduct() }) .subscribe((response) => { console.log('response', response); })

subscribing within a subscribe is a rx anti-pattern. Use .mergeMap() to link the inner and outer observable to eachother.
@MarkvanStraten i have updated answer using flatMap() it's working for me

Eugen Tatuev · Accepted Answer · 2017-11-28 07:57:42Z

Give a try with a bit changed error handling and single subscribe:

 Observable .interval(2000) .switchMap(() => { return this._productService.getProduct(); }) .catch(err => { // handle errors this.errorMsg = <any>err; // rethrow error return Observable.throw(err); // or just return some correct value // return Observable.of(new Product()) }) .subscribe(response => console.dir(response));

UPD: mistake at response logging

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