Relationships - core data

AppDelegate.swift

lazy var managedObjectModel: NSManagedObjectModel = {
  let modelURL =
    NSBundle.mainBundle().URLForResource("myDevices", withExtension: "Momd")!
  return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

lazy var persistentStoreCoordinator:
  NSPersistentStoreCoordinator = {
    
  let coordinator = NSPersistentStoreCoordinator
    (managedObjectModel: self.managedObjectModel)
  let url = self.applicationDocumentDirectory.
    URLByAppendingPathComponent("SingleViewCoreData.sqlite")
  var failureReason = "There was an error creating or loading the application's saved data."

  do {
    try coordinator.addPersistenStoreWithType (NSSQLiteStoreType, 
      configuration: nil, URL: url, options: 
        [NSMigratePersistentStoresAutomaticallyOption: true,
        NSInferMappingModelAutomaticallyOption: true])
  } catch {
    var dict = [String: AnyObject]()
    dict[NSLocalisedDescriptionKey] = "Failed to initialize the application's saved data"
    dict[NSUnderlyingErrorKey] = error as NSError
    let wrappedError = NSError(domain:
      "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)

    NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
    abort()
  }
  return coordinator
}()

lazy var managedObjectContext: NSManagedObjectContext {
  
  
}

code.txt

https://www.youtube.com/watch?v=uJuLk1niBYA

--- add relationships
Device - Owner, Destination - Person, leave optional
Persion - Devices, Destination - Device, Inverse - Owner, not optional, Type - to many
Editor > Create NSManagedObjects Subclass, both

In Devices.swift 
var deviceDescription: String {
  return "\(name) (\(deviceType))"
}

Remember again to remove the question mark from Person - name, devices. Device - all Strings

Device+CoreDataProperties.swift

import Foundation
import CoreData


extension Device {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Device> {
        return NSFetchRequest<Device>(entityName: "Device")
    }

    @NSManaged public var deviceType: String
    @NSManaged public var name: String
    @NSManaged public var owner: Person?

}

DeviceDetailTableViewController.swift

import CoreData
import UIKit

@objcMembers
class DeviceDetailTableViewController: UITableViewController {
    var managedObjectContext: NSManagedObjectContext!
    var device Device?

    @IBOutlet weak var nameTextField: UITextField!
    @IBOutlet weak var deviceTypeTextField: UITextField!
    @IBOutlet weak var deviceOwnerLabel: UILabel!
  
    override func viewWillAppear(animated: Bool) {
      super.viewWillAppear(animated)
            
      if let device = device {
        nameTextField.text = device.name
        deviceTypeTextField.text = device.deviceType
          
        if let owner = device.owner {
            deviceOwnerLabel.text = "Device owner: \(owner.name)"
        } else {
            deviceOwnerLabel.text = "set device owner"
        }
      }
    }
  
    override func viewWillDisappear(animated: Bool) {
        // need to add a device?
        if device == nil {
            if let name = nameTextField.text, deviceType = deviceTypeTextField.text,
                entity = NSEntityDescription.entityForName("Device", 
                inManagedObjectContext: managedObjectContext) where !name.isEmpty
                && !deviceType.isEmpty {
                    device = Device(entity: entity, insertIntoManagedObjectContext:
                        managedObjectContext)
                    device?.name = name
                    device?.deviceType = deviceType
            }
        }
    }
  
    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexpath: 
        NSIndexPath) {
        if indexPath.section == 1 && indexPath.row == 0 {
            if let personPicker =
                storyboard?.instatiateViewControllerWithIdentifier("People") as?
                PeopleTableViewController {
                    
                    // more personPicker setup code here
                    personPicker.pickerDelegate = self
                    personPicker.selectedPerson = device?.owner
                    
                    navigationController?.pushViewController(personPicker, animated: true)
                }
        }
    }
    
    tableView.deselectRowAtIndexPath(indexPath, animated: true)
    }    
}

extension DeviceDetailTableViewController: PersonPickerDelegate {
    func didSelectPerson(person: Person) {
        device?.owner = person
        
        do {
            try managedObjectContext.save()    
        } catch {
            print("Error saving the managed object context!")
        }
    }
}

PeopleTableViewController.swift

import UIKit
import CoreData

protocol PersonPickerDelegate: class {
  func didSelectPerson(person: Person)
}

@objcMembers
class PeopleTableViewController: UITableViewController {
    var managedObjectContext: NSManagedObjectContext!
    var people = [Person]()

    // for person select mode
    weak var pickerDelegate: PersonPickerDelegate?
    var selectedPerson: Person?