Do something when an action has been dispatched

Let's say we an action SyncUserData, which returns observable that listen to changes from the database. Whenever there's a change, the action dispatches the action new PatchUserData(newData).

The SyncUserData action is dispatched (only once) from ngxsOnInit of the state.

In a different section (e.g., component), I want to do something whenever the action PatchUserData is dispatching. Something like this:

this.store.onDispatch(PatchUserData).subscribe();

I was looking a bit in the source, and I didn't find something similar to my example.

Solution

An alternative to subscribing to the state directly is to use the NGXS action stream to be notified when a specific action has been dispatched/completed see the documentation for action handlers.

From the official doco:

@Component({ ... })
export class CartComponent {
  constructor(private actions$: Actions) {}

  ngOnInit() {
    this.actions$.pipe(ofActionSuccessful(CartDelete)).subscribe(() => alert('Item deleted'));
  }
}