Core Data search lists where certain variable equal

Question

It's been a while since I've used Core Data or SQL, so I can't even remember how to do this or even how to search for it.

I have a list of objects

  name | id   |
_______|______|
John   |  4   |
Betty  |  7   |
Betty  |  2   |
Betty  |  4   |
Edward |  2   |
Edward |  4   | 
John   |  4   |

I want to find the id that contains Betty and Edward. This should return 2 Not 4

Any ideas?

Thanks a lot! Alex

Answer 1

You will have a problem with the attribute name id so I use uid. Also, note that the name

NSArray *bettyIDs = [[allPersons filteredArrayUsingPredicate:
  [NSPredicate predicateWithFormat:@"name = %@", @"Betty"]  valueForKeyPath:@"uid"];
NSArray *edIDs    = [[allPersons filteredArrayUsingPredicate:
  [NSPredicate predicateWithFormat:@"name = %@", @"Edward"] valueForKeyPath:@"uid"];

NSArray *commonIDs = [bettyIDs filteredArrayUsingPredicate:
  [NSPredicate predicateWithFormat:@"self in %@", edIDs]];
// commonIDs --> @[@2, @4];