How to create UINavigationBar drop shadow

If you apply a drop shadow to a UINavigationBar, the shadow is clipped at below the corners:

This is just how shadows behave on rectangles. I usually create a path for the shadow that’s a bit wider than the actual nav bar, which creates an effect that is more like what you’d generally expect:

@implementation UINavigationBar (DropShadow)

-(void)willMoveToWindow:(UIWindow *)newWindow {
    [super willMoveToWindow:newWindow];
    self.layer.shadowColor = [UIColor blackColor].CGColor;
    self.layer.shadowOpacity = 1;
    self.layer.shadowOffset = CGSizeMake(0,4);
    CGRect shadowPath = CGRectMake(self.layer.bounds.origin.x - 10, self.layer.bounds.size.height - 6, self.layer.bounds.size.width + 20, 5);
    self.layer.shadowPath = [UIBezierPath bezierPathWithRect:shadowPath].CGPath;
    self.layer.shouldRasterize = YES;
}