Swift update existing item core data - core-data

Question

I have seen many examples with one view controller for adding or updating core data items. Any thoughts on pros or cons of doing in separate view controllers?
My code for trying to do the update I think I am missing one key part to get it to work.
#IBAction func saveItem(sender: AnyObject) {
let appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let context: NSManagedObjectContext = appDel.managedObjectContext!
let en = NSEntityDescription.entityForName("Items", inManagedObjectContext: context)
var existingItem = dataModel.self
if (row > 0) {
println(teaname.text)
existingItem.setValue(teaname.text as String, forKey: "name")
existingItem.setValue(teatype.text as String, forKey: "type")
existingItem.setValue(qty.text as String, forKey: "amount")
existingItem.setValue(temp.text as String, forKey: "temp")
existingItem.setValue(time.text as String, forKey: "time")
} else {
}
context.save(nil)
self.navigationController?.popViewControllerAnimated(true)
}
I get (lldb) with a thread breakpoint at existingItem.setValue(teaname.text as String, forKey: "name")

Answer 1

It does not appear you actually have a specific object to update. I use the following function to fetch an object by its unique ID. Only once you have an object (mine is called Event) can you update it.
func fetchEvent(eventID: Int) -> Event? {
// Define fetch request/predicate/sort descriptors
var fetchRequest = NSFetchRequest(entityName: "Event")
let sortSections = NSSortDescriptor(key: "eTitle", ascending: true)
let sortDescriptor = NSSortDescriptor(key: "eID", ascending: true)
let predicate = NSPredicate(format: "eID == \(eventID)", argumentArray: nil)
var error = NSErrorPointer()
// Assign fetch request properties
fetchRequest.predicate = predicate
fetchRequest.sortDescriptors = [sortSections, sortDescriptor]
fetchRequest.fetchBatchSize = 1
fetchRequest.fetchLimit = 1
// Handle results
let fetchedResults = managedObjectContext?.executeFetchRequest(fetchRequest, error: error)
if fetchedResults?.count != 0 {
if let fetchedEvent: Event = fetchedResults![0] as? Event {
println("Fetched object with ID = \(eventID). The title of this object is '\(fetchedEvent.eTitle)'")
return fetchedEvent
}
}
return nil
}
Once you have fetched an object and have a core data object to update, then you can update it like so.
func updateEvent(eventDict: Dictionary<String, AnyObject>, id: Int) {
if let event: Event = fetchEvent(id) {
println(event)
event.eID = id
event.eTitle = getString(eventDict["title"])
event.eLocation = getString(eventDict["location"])
event.eDescription = getString(eventDict["description"])
event.eStart = getDate(eventDict["startDate"])
event.eEnd = getDate(eventDict["endDate"])
event.eMod = NSDate()
event.eSecID = getSecID(event)
}
}
And then you may want to save your managed object context.