In the context of an Angular component I have 2 observables.

Requirements

1. I want to execute both in sequence.
2. If the first observable fails I don’t want to run the second
3. If either fail, I want to log a single error msg
4. If both succeed, I want to log a single success msg

Approach

• I am using concat to achieve #1 and #2
• I am capturing #3 in the error notification of the concat subscription. There will only ever be 1 error notification to process due to concat
• #4 is where the problem lies. I cannot use next on the concat subscription as it will log a success msg per observable. I can handle this in the complete notification of the concat subscription but that is not typically where you would handle success. There’s a code smell off this approach.

What is the best way to achieve my requirements?

    getData1$ = this.myService.getData1();
    getData2$ = this.myService.getData2();
    
    constructor(private myService: MyService) {
      this.getAllData();
    }
    
    getAllData() {
      concat(this.getData1$, this.getData2$)
      .pipe(finalize(() => console.log('always called')))
      .subscribe(() => {
        error: console.log('one or more data fetches have had an error');
        complete: console.log('all data fetches have succeeded');
      });}