Whenever Apple releases a new version of iOS, Stanford University eventually releases a course telling you how to develop apps in that environment. iOS 10 came out last fall, and now the iOS 10 app development course is getting rolled out this quarter. It's free online, of course, on iTunes.
You can now find "Developing iOS Apps with Swift" housed in our collection of Free Computer Science Courses, which currently features 117 courses in total, including some basic Harvard courses that will teach you how to code in 12 weeks.
As always, courses from other disciplines can be found on our larger list, 1,500 Free Online Courses from Top Universities.