Client-server synchronization over REST

Question

This question is about what I think is a very common problem in Android / iOS development but I haven\'t found any \"standard\" solution yet.

Let\'s say we have a fairly

Answer 1

I don't think there's a silver bullet but the pattern you're looking for is caching. In past projects I have copied items from the server to local storage (SQLite or flat file), and maintained meta-data about the entries to update/upload/purge based on simple rules. It's not a simple problem and ends up being a lot of code.

Consistency: in your example, either ensure you download the countries table first, or make the two operations atomic - e.g., make copies of the "new" tables and only replace your cached versions if both copies complete successfully (doubles up on storage).

Only download new/deleted/changed: Yep, this requires client/server integration - timestamp all the records (with GMT), ask for metadata from the server, and walk through your local metadata deciding what to do. (Hint UUIDs on the rows are helpful).

Synchronize local changes: Yes, more client/server integration. See above paragraph.

Handling all the exceptions and edge cases is challenging. Take a look at the problems with iCloud sync'ing CoreData. Perhaps not a fair comparison, as Apple is trying to solve this for a totally distributed database, but interesting reading nonetheless.