When using auto layout, retrieving subview frames should be done after frames are determined based on constraints

gistfile1.txt

In UIViewController subclasses
-(void)viewDidLayoutSubviews
{
    self.containerView.frame = self.view.bounds;
    self.currentVC.view.frame = self.containerView.bounds;
}

In UIView subclasses
-(void)layoutSubviews
{
    [super layoutSubviews];
    //accessing frame should be done in layout Subviews
    self.thumbnailButton.layer.cornerRadius = 0.5 * CGRectGetWidth(self.thumbnailButton.frame);
}