title: How to use RxSwift Observable<Int>.interval?
body: <p>I'm trying to emit a sequence on a ”pulse” at a given time interval. Totally new to everything Rx, but thought this would do it:</p>
  
  <pre><code>import RxSwift
  let db = DisposeBag()
  
  _ = Observable&lt;Int&gt;.interval(1.0, scheduler: MainScheduler.instance)
      .debug("interval")
      .subscribe(onNext: {
          print($0)
      })
      .addDisposableTo(db)
  </code></pre>
  
  <p>But it only outputs:</p>
  
  <pre><code>2017-09-25 06:12:41.161: interval -&gt; subscribed
  </code></pre>
  
  <p>And nothing more. What am I not understanding here?</p>