Apple has documented certain APIs. Others they have not documented. They call all class interfaces and view hierarchies "private apis" and forbid access to tho

Apple has documented certain APIs. Others they have not documented. They call all class interfaces and view hierarchies "private apis" and forbid access to those APIs by developers. If you use them and apple figures it out, no app store for you. There is really little difference between the private and public APIs other than the fact Apple has or hasn't blessed them for use.