How to “touch” a Core Data entity, to trigger NSFetchedResultsController?

Question

Say you have a core data entity,

public class CDPerson: NSManagedObject

You get new info from the net ... a field changes,

p.n         


        

Answer 1

Core Data recognizes changes by the firing of -willChangeValueForKey: and -didChangeValueForKey: as the comment from @pbasdf indicated. You can call only -didChangeValueForKey: if you want but I would really do both.

Those calls also work on relationships. So in your Address object, you can touch both the value to be changed and the relationship to the person:

- (void)setCity:(NSString*)cityString
{
  [self willChangeValueForKey:@"city"];
  [self willChangeValueForKey:@"person"];
  _city = cityString;
  [self didChangeValueForKey:@"person"];
  [self didChangeValueForKey:@"city"];
}

With an end result of the NSFetchedResultsController being told that the associated person object has changed and the cell should be re-drawn.