Angular http client observable pipe map

Question

I have this in my service

  doSomething(): Observable<any> {
    return this.http.get('http://my.api.com/something')
      .pipe(
        map((data: Response) => {
            if (data && data['success'] && data['success'] === true) {
              return true;
            } else {
              return false;
            }
          }
        )
      );  
  }

This works, I can subscribe to the function from my component, for example

    this.myService.doSomething().subscribe(
        (result) => {
            console.log(result);
        },
        (err) => {
            console.log("ERROR!!!");
        }
    );

Al this already works, but I want to refactor so that I can remove

 if (data && data['success'] && data['success'] === true)

in my map. So that the map function only will be executed when I have upfront did the check. My first thought was to add a function in the pipe stack that will take the Response from the http client, check if the the conditions are good, otherwise throw an error (with throwError function). But I'm struggling how to (well at least figure out which Rxjs function to use).

Can somebody help me out with this?

rguerin · Accepted Answer · 2018-10-29 16:48:31Z

1

Try using this :

doSomething(): Observable<any> {

    return this.http.get('http://my.api.com/something')
      .pipe(
        mergeMap((data: Response) => {
            return of(data && data['success'] === true) 
          }
        ));  
}

You have to perform the mergeMap first to do the check as your observable result will not be available if not...

edited Oct 29, 2018 at 16:48

answered Oct 29, 2018 at 16:38

rguerin

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1 Comment

fransyozef Over a year ago

Yes .. it worked , I have a helper export function checkServerSuccessResponse(data: Response): Observable<any> { return (data && data['success'] === true) ? of(data) : throwError("server responded false"); } so when the first condition is false, it will throw an error. if the condition is true, the data object is passed to the normal map

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