等待两个 Observable 完成

Question

I want to call a method after two Observables have returned values. I did some searching and it seems like forkJoin is what I want, but I can't get it to work. I know both of these Observables are returning values, as I am using the data for each individually elsewhere in the component, so clearly I'm doing something else wrong.

Here is what I tried. I'm using rxjs v6.4.

forkJoin(
  this.store.pipe(select(fromStore.getAppointmentsLoading)),
  this.clientStore.pipe(select(fromClientStore.getClientsLoading)),
).subscribe(
  ([res1, res2]) => {
    console.log('res1', res1);
    console.log('res2', res2);
  },
  err => console.error(err),
);

Nothing is logging to the console and I am not getting any errors. Again, the Observables I am passing in are definitely returning values.

Am I doing something wrong, or am I taking the wrong approach entirely by using forkJoin ?

Answer 1

forkJoin emits when all the observables complete (or when one of them throws an error), not when they emit.

You can use combineLatest instead.

Be careful to not import the instance operator from 'rxjs/operators' . It's a common mistake caused by some IDEs auto-import feature. In this case, we need the static version, imported from 'rxjs' :

import {combineLatest} from 'rxjs';

combineLatest([
  this.store.pipe(select(fromStore.getAppointmentsLoading)),
  this.clientStore.pipe(select(fromClientStore.getClientsLoading)),
]).subscribe(
  ([res1, res2]) => {
    console.log('res1', res1);
    console.log('res2', res2);
  },
  err => console.error(err),
);