title: How to make RACSignal to become hot?
body: <p>ReactiveCocoa can convert the signal to "hot" signal by calling its <code>-subscribeCompleted:</code>. But I think this method is quite verbose if you do not care about the result (i.e. no subscribers).</p>
  
  <pre><code>RACDisposable *animationDisposable = [[self play:animation] subscribeCompleted:^{
      // just to make the animation play
  }];
  </code></pre>
  
  <p>And these 3 lines are not expressive enough to show my intention.</p>
  
  <p>Is there any method for similar purpose? Thanks!</p>