Variable instantiated in prepare for Segue has nil properties in ViewDidLoad - ios

Question

My view controller is loading before Core Location data is available from the model.
I've a Master View controller that modally pushes a new view controller with two NSManagedObject subclasses - records and locations - which are instantiated in a prepareForSegue method.
if segue.identifier == "newRecord"
{
let controller = (segue.destinationViewController as! NewRecordVC)
let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate // instantiate the delegate methods in AppDelegate
let managedContext = appDelegate!.managedObjectContext // create context from delegate methods
let recordEntity = NSEntityDescription.entityForName("RecordData", inManagedObjectContext: managedContext)
let locationEntity = NSEntityDescription.entityForName("Location", inManagedObjectContext: managedContext)
controller.location = Location(entity: locationEntity!, insertIntoManagedObjectContext: managedContext)
controller.record = Record(entity: recordEntity!, insertIntoManagedObjectContext: managedContext)
controller.managedContext = appDelegate?.managedObjectContext
print("segueing")
}
Both managed objects have inits for various values. Records have simple pre-assigned values assigned to properties that show up on the new view. Location properties, however, mainly require location services to assign property values. Printing property values shows that while a location is instantiated in viewDidLoad, the location properties assigned by location services are still nil. Location services are working - the properties print from within the model, BUT this is after viewDidLoad. On load, I need at least the geoPlacemark property, which provides text for the view.
override func viewDidLoad()
{
super.viewDidLoad()
...
if let recordNotNil = record
{
...
iD.text = "ID: \(recordNotNil.iD)"
}
if let locationNotNil = location
{
...
print("bing")
print(locationNotNil.temp)
record!.location = location!
print(location.geoPlacemark)
print(location.timestamp)
if let geoPlacemarkNotNil = location.geoPlacemark
{
print("bong")
locationText(geoPlacemarkNotNil)
}
}
}
Do I have to run the location services from within every view controller, not the model? Or is there a way to get the view to wait for the location delegate methods?

Answer 1

In prepareForSegue() the destinationViewController is already instantiated, and viewDidLoad() was already called.
If you want to set a label you should really do it in viewWillAppear()
override func viewWillAppear() {
super.viewWillAppear()
// Set up your views here
}
The other benefit of viewWillAppear() over viewDidLoad() is that it's called every time the ViewController is about to show up, which can be multiple times during the VCs lifecycle - as opposed to a single call ad the beginning of the VC's lifecycle of viewDidLoad().

Answer 2

The problem here came from using the normal override init method for the NSManagedObject.
class Record: NSManagedObject
{
override init(entity: NSEntityDescription, insertIntoManagedObjectContext context: NSManagedObjectContext?)
{
super.init(entity: entity, insertIntoManagedObjectContext: context)
let randomBit = String(arc4random_uniform(100))
iD = NSDate().toIDTimeDateString() + "-" + randomBit + "OtR"
believers = 0
deviceTime = NSDate()
doubters = 0
eventTimeStarted = NSDate()
eventTimeEnded = NSDate()
featureImageIndex = 0
coreLocationUsed = 0
photoTaken = 0
tableSection = "My Records"
timeRecorded = deviceTime
validationScore = 0
}
}
As per the apple doc.s, custom NSManagedObjects should be initiated using awakeFromInsert or awakeFromFetch.