Moving navBar with scrollViewDidScroll:

gistfile1.m

typedef NS_ENUM(NSInteger, ScrollDirection)
{
  ScrollDirectionDown = -1,
  ScrollDirectionNone,
  ScrollDirectionUp
};

###################################

[RPMDefines statusBarSize].height = 20;
_defaultNavHeight = 44. + 20.;

###################################      
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
  RPMDbgLog(@"navBar originY: %f", _navBar.frame.origin.y);
  ScrollDirection direction = (scrollView.contentOffset.y > _lastContentOffsetY) ? ScrollDirectionDown : ScrollDirectionUp;
  if (scrollView.contentOffset.y == _lastContentOffsetY)
    direction = ScrollDirectionNone;
  _scrollDirection = direction;
  _lastContentOffsetY = scrollView.contentOffset.y;
  
  // navBar adjustments on scroll
  CGFloat originY = _navBar.frame.origin.y;
  CGRect navBarFrame = _navBar.frame;
  
  CGFloat alpha = (ABS([RPMDefines statusBarSize].height - _defaultNavHeight) + originY) / ABS([RPMDefines statusBarSize].height - _defaultNavHeight);
  _navItem.titleView.alpha = alpha;
  
  if ((scrollView.contentOffset.y > -_defaultNavHeight))
  {
    if (_scrollDirection == ScrollDirectionUp)
    {
      originY++;
      
      if (originY > 0)
      {
        originY = 0;
      }
    }
    else if (_scrollDirection == ScrollDirectionDown)
    {
      originY--;
      if (originY < [RPMDefines statusBarSize].height - _defaultNavHeight)
      {
        originY = [RPMDefines statusBarSize].height - _defaultNavHeight;
      }
    }
    navBarFrame.origin.y = originY;
    _navBar.frame = navBarFrame;
  }
  else
  {
    navBarFrame.origin.y = 0;
    _navBar.frame = navBarFrame;
  }
}