prepareForSegue empties my NSManagedObject Array - ios

Question

I need to pass data from one view to another in the current app I'm working on with the latest version of Swift for iOS 8. I fill the FacultyArray using a function that gets the information from CoreData using MagicalRecord. The problem I encounter is that, when I try to use the filled array in the prepareForSegue function turns out it's empty.
import UIKit
import SwiftyJSON
class EspecialidadTVC: UITableViewController {
let defaults = NSUserDefaults.standardUserDefaults()
let endpoint = Connection()
var facultyList:Array<Faculty>? = TR_Faculty().get()
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources thavaran be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
//return self.facultyArray!.count
return (self.facultyList?.count)!
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("facultyCell", forIndexPath: indexPath)
cell.textLabel?.text = self.facultyList![indexPath.row].nombre
return cell
}
/*
// Override to support conditional rearranging of the table view.
override func tableView(tableView: UITableView, canMoveRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return false if you do not want the item to be re-orderable.
return true
}
*/
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "presentMainMenuSegue" {
let splitViewController:MasterSVC = segue.destinationViewController as! MasterSVC
let indexpath = self.tableView.indexPathForSelectedRow
splitViewController.faculty = self.facultyList![indexpath!.row]
//splitViewController.modalTransitionStyle = UIModalTransitionStyle.FlipHorizontal
}
if segue.identifier == "logoutSegue" {
}
}
}
Is there a better way to send an NSManagedObject between views?
UPDATE
Here's the destination code for MasterSVC. There's no console error, just that my array gets emptied, so when I send the object, this is a nil object.
import UIKit
import Foundation
class MasterSVC: UISplitViewController {
var faculty:Faculty!
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.leftBarButtonItem = splitViewController?.displayModeButtonItem()
navigationItem.leftItemsSupplementBackButton = true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
}
}
UPDATE 2
Method that fills the array
class TR_Faculty {
let dateFormatter = NSDateFormatter()
func store(json: JSON) {
//Clear previous data
Faculty.MR_truncateAll()
for (index,subJson):(String, JSON) in json {
let fac = Faculty.MR_createEntity()
fac?.id = Int(subJson["IdEspecialidad"].stringValue)
fac?.codigo = subJson["Codigo"].stringValue
fac?.nombre = subJson["Nombre"].stringValue
fac?.descripcion = subJson["Descripcion"].stringValue
fac?.updated_at = self.dateFormatter.dateFromString(subJson["updated_at"].stringValue)
}
NSManagedObjectContext.MR_defaultContext().MR_saveToPersistentStoreAndWait()
}
func get()-> Array<Faculty>?{
return Faculty.MR_findAll() as! Array<Faculty>
}
}

Answer 1

Well the problem that I had is that the call to the service is asynchronous, so nothing guarantees that the call is gonna finish before you perform a segue to another view controller. What worked for me is just placing performSegueWithIdentifier inside the success part of the call.
As a tip for other people just starting to use API's in mobile applications, when you wanna call a restful API from your app, you should make the call, wait until it successfully finishes and then populate the SQLite database. Afterwards you can make the call to the database to populate the view.