Deleting many to many relationship coredata - ios

Question

I have a many to many relationship of "BillSplitters" to "Items", im trying to. Delete a billsplitter from a tableview of billsplitters, but when i look at my items they still list the billsplitters they are related to and havent been deleted. I have tried changing the delete rule from nullify to cascade on both items and bill splitters but nothing seems to be changing.
Heres the code that i think is relevant:
BillSplitter table view:
func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
let billSplitter = allBillSplitters[indexPath.row]
let currentSplitters = self.bill.mutableSetValueForKey("billSplitters")
let managedContext = self.bill.managedObjectContext
removeBillSplitter(billSplitter)
currentSplitters.removeObject(billSplitter)
do {
try managedContext!.save()
}
catch let error as NSError {
print("Core Data save failed: \(error)")
}
print(currentSplitters)
tableView.reloadData()
}
}
func removeBillSplitter(billSplitter: BillSplitter) {
if let index = allBillSplitters.indexOf(billSplitter) {
allBillSplitters.removeAtIndex(index)
}
}
Items Tableview:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
fetchBillItems()
let cell: NewBillSplitterItemCell = tableView.dequeueReusableCellWithIdentifier("NewBillSplitterItemCell") as! NewBillSplitterItemCell
let item = allItems[indexPath.row]
let numberOfSplitters = item.billSplitters?.count
if numberOfSplitters == 0 {
cell.currentSplitters.text = "No one is paying for this item yet."
} else {
var splitterList = "Split this item with: "
let itemSplitters = item.billSplitters?.allObjects as! [BillSplitter]
for i in 0...Int((numberOfSplitters)!-1) {
splitterList += "\(itemSplitters[i].name!), "
}
cell.currentSplitters.text = splitterList
}
cell.name.text = item.name
cell.price.text = "£\(item.price!)"
return cell
}
The idea is to select items from the item tableview to assign to a billsplitter, which works fine then redirects to the billsplitter table view, when deleting a billsplitter from this table view it works fine and is no longer listed, but when going back to the items table view it still lists the billSplitters when iterating over the itemSplitters for loop and i dont understand why? Do i have to find each item associated with the bill splitter and delete them from there? I though thats what cascade would do?