title: NSTimer sometimes freezes when app is doing heavy computation
body: <p>I'd like to animate some loading points while the app is doing some computation in the background. I achieve this via an <code>NSTimer</code>:</p>
  
  <pre><code>    self.timer = [NSTimer scheduledTimerWithTimeInterval:0.3f
                                               target:self 
                                             selector:@selector(updateLoadingPoints:) 
                                             userInfo:nil 
                                              repeats:YES];
  </code></pre>
  
  <p>Unfortunately, sometimes, when the computation becomes pretty heavy, the method is not fired and the updating therefore doesn't happen. It seems like all the firing is in a queue which is fired after the heavy computation.</p>
  
  <p>Is there a way to give the <code>NSTimer</code> a higher priority to ensure that it's regularly calling my method? Or is there another way to achieve this?</p>