title: Why does Apple recommend us to not invoke viewWillLoad, viewWillAppear, viewDidDisappear, etc.?
body: <p>I'm following an exercise from a book and we're building out the view controllers programmatically and creating unit tests. The book also says this, and from previous experience with reading Apple reference docs, Apple references always say to not invoke viewDidLoad, viewWillAppear, viewDidDisappear, etc directly.  I'm curious to know why this is and what happens if we do?</p>