Apple and private APIs

Question

Now that it's public knowledge that App Store submissions are being tested for use of private APIs, I need to ask the question... what exactly is a private API so that I may avoid them?

Answer 1

My app was rejected by apple because of using private API.Here is code,

    Class UIKeyboardImpl = NSClassFromString(@"UIKeyboardImpl");

    id activeInstance = [UIKeyboardImpl performSelector:@selector(activeInstance)];

    [activeInstance performSelector:@selector(dismissKeyboard)];