If you are like me you probably have searched for clues to and found little... particularly when confronted by the errors as you unravel how this works.  Okay a slight exaggeration, there are snipets of info that people have solved this annoying issue in  making comments work in Drupal 8 REST services. The lack of collective information in resolving issues has meant hours of debugging and working through core code to understand what is actually happening.  If you want to...

During the process of building the app, there are warnings about the code.  It's good practice to remove all warnings before you submit your apps to the App Store so there's a few steps you can follow to silence these warnings: Navigate the the Project Settings page below; Select the drop down menu next to Devices; Change from Universal to iPhone; then Run your app again and the warnings should disappear.