I can not figure it out why i got this error

  getByURL(url: string): any {
    return this.apiService.get(url).pipe(map(data => data));
  }

  getByNextPage(): Observable<any> {
    const url = 'url';
    this.getByURL(url).pipe(
      expand(data => {
        console.log(data);
      })
    );
  }

I got this error at line that has expand(data => ... . I want to use expand() so i can recursive the call for the next api.

Type 'void' is not assignable to type 'ObservableInput<{}>'

Any hint would be really appreciate. Thanks

I can not figure it out why i got this error

  getByURL(url: string): any {
    return this.apiService.get(url).pipe(map(data => data));
  }

  getByNextPage(): Observable<any> {
    const url = 'url';
    this.getByURL(url).pipe(
      expand(data => {
        console.log(data);
      })
    );
  }

I got this error at line that has expand(data => ... . I want to use expand() so i can recursive the call for the next api.

Type 'void' is not assignable to type 'ObservableInput<{}>'

Any hint would be really appreciate. Thanks

• javascript
• angular
• typescript
• rxjs
• ngrx

Share Follow asked May 31, 2019 at 0:32 daniel8xdaniel8x 1,08044 gold badges2020 silver badges3838 bronze badges 2

• Try adding a return statement to getByNextPage() b/c is not returning anything, – artemisian Commented May 31, 2019 at 0:53
• @artemisian Thanks. stackoverflow./questions/56398014/…. I have another question here which related to this one. Not sure if you can take a quick look. I got stuck there. thanks – daniel8x Commented May 31, 2019 at 15:59

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3 Answers 3

Sorted by: Reset to default 2

You need check data type of data variable and return data in your method.

getByNextPage(): Observable<any> {
    const url = 'url';
    this.getByURL(url).pipe(
      expand(data => {
        console.log(data);
        return data;
      })
    );
  }

expand(data => {
  console.log(data);
})

Your function does not return anything, hence the void. You need to return an observable.

That is because you are using expand() operator badly. If you check documentation, the expand() operator has to return an Observable and you are not returning nothing.

Even though you return "data" variable the error will still persist because that rule.

Check this documentation