This is just a note on the documentation and starter folder. In Chapter 8, we were told to create a swift file called DogPatch.swift. It contained the class DogPatchClient. The starter folder for Chapter 9 still has a swift file named DogPatch.swift. But the Chapter 9 documentation refers to DogPatchClient.swift, not DogPatch.swift. And the final folder for chapter 9 does contain a DogPatchClient.swift. I renamed the file in the starter folder to DogPatchClient.swift and everything seems to work.
Hope this helps,