CoreData to Array in Swift - objective-c

Question

I am trying to fetch data from CoreData and return it as an array for charting in a popular charting library. The code below runs fine and I can print the data to the console, however I want to fill self.hkdataBase with the entries within CoreData and Return it. Any idea what I am doing wrong ?
class ViewController: UIViewController {
var hkdataBase = [HKdataBase]()
....
func fetchCoreData () -> NSArray {
//Setting up Core Data
var context = (UIApplication.sharedApplication().delegate as AppDelegate).managedObjectContext!
var request = NSFetchRequest(entityName: "HKdataBase")
request.returnsObjectsAsFaults = false
//Fetching Data
self.hkdataBase = context.executeFetchRequest(request, error: nil)! as [HKdataBase]
if hkdataBase.count > 0 {
for i in hkdataBase {
**I WANT TO FILL self.hkdataBase WITH i ELEMENTS HERE ** -> println(i.hr_data) WORKS FINE
}
} else {
println("No results")
}
}
**return self.hkdataBase with elements**
}
UPDATE 1:
I want to Return an Array from the fetched data in CoreData. The hr_data are Heart Rate measures and hr_date are the associated NSDate. The HKdataBase looks like this:
import Foundation
import CoreData
class HKdataBase: NSManagedObject {
#NSManaged var hr_date: NSDate
#NSManaged var hr_data: NSNumber
}

Answer 1

After the fetch, you already have your managed objects in self.hkdataBase. Managed objects are KVC compliant, so to get just one kind of value out if it is quite simple.
var hrData = (self.hkdataBase as NSArray).valueForKey("hr_data") as NSArray
You now have an array containing your hr_data, presumably an array of NSNumber objects.