Adding One CoreData List to Another - ios

Question

Let's say there are two favorite food lists: Johnny's List and Jane's List. They are both in CoreData, are separate entities, but have identical attributes. Both have four attributes: food name, secret ingredient, rating, and where to get it.
The user taps a button to merge the two lists. Specifically, Jane's list should now show up in Johnny's BUT her items should go first.
A very simple example set of lists:
Pre Merge - Johnny's List (only has 1 record)
Apple Pie -
Apples -
4.5 -
Susan's Diner
Pre Merge - Jane's List (has 2 records)
Turkey Dinner -
Turkey -
5.0 -
Mom's house -
BBQ Dinner -
Pulled Pork -
4.0 -
Route 6 Rib Shack
Post Merge - Johnny's List (has 3 records)
Turkey Dinner -
Turkey -
5.0 -
Mom's house
BBQ Dinner -
Pulled Pork -
4.0 -
Route 6 Rib Shack
Apple Pie -
Apples -
4.5 -
Susan's Diner
Johnny's new list of 3 items should save over Johnny's old list in CoreData. Jane's list should be cleared.

Answer 1

Solved!
There are likely several ways to solve this question but what I received for answers and found online weren't doing the trick. I took a shot at just writing the code and it works!
My Code
Here's my merge function.
It is passed only one parameter: the destination name. That is because my source list context was already setup outside the function.
Alternatively you could pass two parameters, the name of List A and List B, and set both contexts up in the function.
My CoreData fetch also has a sort predicate which you might not need.
func merge_ListA_Into_ListB (targetList: String) {
//Setup Targetlist context
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext!
//Get sorted CoreData list and assign it to targetList_Cntxt
let fetchRequest = NSFetchRequest(entityName: targetList)
let sortDescriptor = NSSortDescriptor(key: "displayOrder", ascending: true)
fetchRequest.sortDescriptors = [ sortDescriptor ]
do {
let fetchedResults = try managedContext.executeFetchRequest(fetchRequest) as? [NSManagedObject]
if let results = fetchedResults {
targetList_Cntxt = results
}
} catch { print(error) }
for i in (0..<listA_Cntxt.count).reverse() {
//Grab a ListA task item
let itemToMove = listA_Cntxt[i]
//Assign the ListA item's contents to variables
let nameToTransfer = itemToMove.valueForKey("name") as? String
let descToTransfer = itemToMove.valueForKey("desc") as? String
//Assign the ListA item's contents to the target's object
let newItem = NSEntityDescription.insertNewObjectForEntityForName(targetList, inManagedObjectContext: managedContext)
newItem.setValue(nameToTransfer, forKey: "name")
newItem.setValue(descToTransfer, forKey: "desc")
//Insert the item!!
targetList_Cntxt.insert(newItem, atIndex: 0)
}
//Calls function that updates each records sort/display #
update_TargetDisplayOrder()
try! managedContext.save()
print("List merged into \(targetList).")
}
Good luck!