I am curious as to what is the purpose of writing extensions for a class that you can already add code?
For example, in Ray Wenderlich's AlamoFire tutorial,
He has a ViewController class, but he writes an extension for that ViewController for his Networking Functions and
This is something Apple does too. If you look at the code (let's say the
Array struct) you can see that every conformance to a protocol is encapsulated inside an extension.
The only difference is that your code is better separated. But it really is up to you.