I am trying to save CLLocation
data in Core Data. My property is set as a Transformable object.
Some sample code out there indicates one can save the location data using this objc converted to an NSValue
.
CLLocationCoordinate2D myLocation;
NSValue *locationValue = [NSValue valueWithBytes:&myLocation objCType:@encode(CLLocationCoordinate2D)]
// then put locationValue into storage - maybe an ObjC collection class or core data etc.
Retrieving the object from the data store is supposed to work using this paradigm.
CLLocationCoordinate2D myLocation;
NSValue *locationValue = // restored from your database or retrieved from your collection class
[locationValue getValue:&myLocation];
I am attempting to extrapolate on this idea and capture the entire CLLocation
object into an NSValue
stored in CoreData
, with the goal to recover the CLLocation
object from the store at a later time.
While testing various methods I have found nil returned when trying to unwrap a CLLocation
object from a Core Data Store. I am placing a CLLocation
object into the store using the following:
//verified that I have a good CLLocation here
newManagedObject.setValue(location as CLLocation, forKey: "location")
Later I attempt to unwrap the CLLocation
let location = detail.valueForKey("location")! as CLLocation
But I find that the object does not unwrap properly.
The unwrapped object looks like:
(CLLocation) location = 0x00007fff59537c90 {
ObjectiveC.NSObject = {}
}
So any use of the CLLocation
object at this point returns the "found nil... error"
Am I missing something obvious about storing/retrieving CLLocation
objects using Swift?
UPDATE
Daniel's answer helped me realize that NSValueTransformer was not going to work for me so I went back to an approach I've used before. Basically encode the object graph using NSKeyedArchiver. My goal, as always, is to use the simplest possible solution so I chose not to use managed object subclasses since the properties I need are already in the existing CLLocation object. I changed the transformable field to Binary Data with the option checked (Store in External Record File). I set out to test this process with minimal changes to the master detail template.
//assuming location is a valid CLLocation and data model has a binary data field
let archivedLocation = NSKeyedArchiver.archivedDataWithRootObject(location)
newManagedObject.setValue(archivedLocation, forKey: "location")
On the main vc as part of the default prepare for segue the data is recovered via the fetch controller.
let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as NSManagedObject
let controller = (segue.destinationViewController as UINavigationController).topViewController as DetailViewController
controller.detailItem = object
On the detail vc I unwrap my object graph using NSKeyedUnarchiver
var lc = NSKeyedUnarchiver.unarchiveObjectWithData(detail.valueForKey!("location") as NSData) as CLLocation
What you are missing is that NSValue is for storing types, i.e., contiguous blocks of memory, not objects. CLLocation is an object.
In order to store a CLLocation in core data, you will have to store each of the properties. An alternative is to use a Coder.