Create one-time subscription

Question

I need to create a subscription to an Observable that is immediately disposed of when it is first called.

Is there something like:

obser         


        

Answer 1

To supplement @Brandon's answer, using first() or the like is also essential for updating a BehaviorSubject based on its Observable. For example (untested):

var subject = new BehaviorSubject({1:'apple',2:'banana'});
var observable = subject.asObservable();

observable
  .pipe(
    first(), // <-- Ensures no stack overflow
    flatMap(function(obj) {
      obj[3] = 'pear';
      return of(obj);
    })
  )
  .subscribe(function(obj) {
    subject.next(obj);
  });