iOS How to put scrollView inside scrollView but not allow the internal scrollView to scroll the external?

Question

In my app I have a modal View Controller that gets dismissed by dragging the screen down, but in the center of that screen I have UITextView. The problem is that when I scroll to the top of the textView and drag its content down the View Controller gets dismissed. How can I avoid that? I would like the external scrollView to scroll independtly of the textView. I used title like that because I suspect it's the same problem, but please correct me if I'm wrong