title: Why is UIView alpha animation slow from 1 to 0 compared to 0 to 1?
body: <p>I have a custom view which I need to hide/unhide with animation.
  UIView animations are not working on hidden property.</p>
  
  <p>So I have overridden setHidden where I modify the alpha with animation.</p>
  
  <p>It works but while hiding it always seem to be slower than the rate at which it appears. I am giving 0.3 as duration but still disappearing happens slowly...
  and when it appears, its fast!</p>
  
  <p><strong>My Code</strong></p>
  
  <pre><code>/* Will modify alpha instead of hidden var */
  -(void)setHidden:(BOOL)hidden
  {
  
      [UIView animateWithDuration:0.5 animations:^{
          self.alpha = hidden?0.0:1.0;
      }];
  
  
  }
  
  /* need to override this so that, .hidden returns value based on alpha as we are not modifying the hidden ivar */
  -(BOOL)isHidden
  {
  
      return (self.alpha == 0.0);
  }
  </code></pre>