I haven't started this yet and have never worked with Core Data before, but was wondering if I was to write companion flavors of my ios / mac osx apps for linux/windows/android, could I still use core data for the main persistence of my application across these platforms? Related question: is there a universal way to access core data from a web API ? Or should I just go with S3 for all this?
Can Core Data be accessed from other platforms?
If you’re asking whether Core Data is a good choice for a local object persistence across platforms, no.
If you’re looking for remote data or object persistence, S3, Firebase, and other options exist.
There are frameworks such as Parse that avoid being tied into one backend hosting vendor, as well.
Programming language choices and local or backend data storage choices all factor into these decisions.