Allows you to slide your navigation bar away when hiding it

MyNavigationController.m

// Header:

@interface MyNavigationController : UINavigationController

- (void)setNavigationBarSlidAway:(BOOL)slidAway animated:(BOOL)animated;

@end

// Implementation:

static int kNavHeight = 64;

@implementation MyNavigationController {
  BOOL _navBarSlidAway;
}

- (void)viewDidLayoutSubviews {
  [super viewDidLayoutSubviews];
  
  [self layoutNavBar];
}

- (void)layoutNavBar {
  self.navigationBar.frame = CGRectMake(0,
    _navBarSlidAway ? -kNavHeight : 0,
    self.view.bounds.size.width,
    kNavHeight);
}

- (void)setNavigationBarSlidAway:(BOOL)slidAway animated:(BOOL)animated {
  _navBarSlidAway = slidAway;
  if (animated) {
    [UIView animateWithDuration:.3 animations:^{
      [self layoutNavBar];
    }];
  } else {
    [self layoutNavBar];
  }
}

@end