Combining 2 values into a NSPredicate - ios

Question

I'm trying to do a fetch request that checks for 2 things.
Here is my Data:
Person - entity
Statement - entity
The Person entity has a relationship to statements as To Many. The statement entity has an attribute called amountOwed. This is the property I want to check in the predicate.
EDIT
What I am trying to do is this.
Check all of my Persons entities for a name, lets say Bob.
Once I find the Bob entity I want to check all of his Statement entities for an attribute called amountOwed and see if it's greater or less then 0.
Check for a name in the Person Entity. When that name matches, use that entity.
Check if the amountOwed in a Statement entity is greater or less then 0.
This is what I have been trying to get to work.
let fetchRequest: NSFetchRequest<Person> = Person.fetchRequest()
fetchRequest.predicate = NSPredicate(format:"name == %# AND #statement.amountOwed >= 0", personName))
let sort = NSSortDescriptor(key: #keyPath(Person.name), ascending: true)
fetchRequest.sortDescriptors = [sort]
positiveFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: coreDataStack.managedContext, sectionNameKeyPath: nil, cacheName: nil)
do {
try positiveFetchedResultsController.performFetch()
} catch let error as NSError{
print("Fetching error: \(error), \(error.userInfo)")
}
I am getting this error:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'to-many key not allowed here'
I found the AND method here: using AND link
Edit

Answer 1

You should build your FRC to fetch Statement objects, not Person objects:
let fetchRequest: NSFetchRequest<Statement> = Statement.fetchRequest()
Assuming the statement relationship has an inverse (to-one) relationship named person, then you can use the following predicate to ensure you fetch only the statements with a positive amountOwed relating to a person with a given name:
fetchRequest.predicate = NSPredicate(format:"person.name == %# AND amountOwed >= 0", personName)
(and similarly for the negative amountOwed). Specify sort descriptors to get whatever sort order you wish. Your FRCs' fetchedObjects arrays will then contain Statement objects which you can use to populate the table view: the positive FRC for section 0 and negative FRC for section 1 (or vice versa).
NB. because you are fetching the Statement objects, it is possible to achieve what you want with just one FRC - but only if you are happy with the statements being sorted by amountOwed (ascending or descending). If you wish to do this, I can provide further detail.

Answer 2

Try this:
NSPredicate(format:"name == %# AND statement.#amountOwed >= 0", personName)
The AND has to be part of the string as the example you attached...