function
willMove(toSuperview:)
invalidateIntrinsicContentSize()
UIResponder.reloadInputViews()
UITextView.deleteBackward()
__dispatch_assert_queue
property
noIntrinsicMetric // -1
UITextView.inputView // The custom input view to display when the text view becomes the first responder.
beginFromCurrentState // start all views from current value, not initial value
class
UITextView
UIInputView
