NSFetchedResultsControllerDelegate and Swift 3 - not calling didChange methods

Question

I'm working on a Core Data App. I'm using Xcode 8.2.

Not all the change methods of the NSFetchedResultsControllerDelegate are not being called for changing objects. (i.e. when I insert a new object into the context)

Does anyone know why this might be? To verify I haven't made a typo, I even copy-pasted that from a typical Master-Detail Application Template.

I'm hoping to animate the tableview rows.

// works
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)

// DOESN'T WORK!!
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>,
                didChange anObject: Any,
                at indexPath: IndexPath?,
                for type: NSFetchedResultsChangeType,
                newIndexPath: IndexPath?)

// WORKS
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)

Answer 1

I figured out what the problem was. I'm using a baseclass (say) MyFetchedResultsControllerTableViewDataSource, where a NSFetchedResultsController is instantiated and who's delegate is specified to 'self'.

The problem is that the baseclass wasn't implementing those methods where subclasses were. I had to make a default implementation in the baseclass then override, then it worked.

This is different to objective-C, which would check at runtime for optional method implementations with 'respondsToSelector'...