How to have a separate error handling for each function in combineLatest?

Question

I need to handle each function's error scenario in this combineLatest. I'll add the code below

const combined = combineLatest(
  this.myservice1.fn1(param),
  this.myservice2.fn2(), 
  this.myservice3.fn3());

const subscribe = combined.subscribe(
  ([fn1,fn2, fn3]) => {
    // operations i need to do
  },
  // how to handle error for fn1, fn2, fn3 separately
  (error) => {
  }
);

Any help would be appreciated!

Answer 1

You can catch errors for each source Observable before using combineLatest latest and eventually rethrow it if you want to handle them later or transform them to a different error:

combineLatest(
  this.myservice1.fn1(param)
    .pipe(
      catchError(err => {
        if (err.whatever === 42) {
          // ... whatever
        }
        throw err;
      }),
    ),
  this.myservice2.fn2()
    .pipe(
      catchError(err => /* ... */),
    ),
  ...
)