Retrieving Core Data With Swift - ios

Question

Problem
I am new to IOS development, and have been struggling with Core Data. I am trying to create a settings page with a switch. I need to remember if this switch is turned on or off. I created a core data application, and have managed to figure out how to save the value of the switch to the attribute. The code below does this, I just can't figure out how to get the saved value of the switch back as on or off. How would I do this? Thanks!
Picture of Core Data
Code:
import UIKit
import CoreData
class preferencesStuff: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
var request = NSFetchRequest(entityName: "Settings")
request.returnsObjectsAsFaults = false;
var results:NSArray = context.executeFetchRequest(request, error: nil)!
if(results.count > 0){
if results[results.count-1] as NSObject == 1 {
println("ON")
}
}else{
println("NO RESULTS")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBOutlet weak var fractSwitchValue: UISwitch!
#IBAction func fractSwitch(sender: AnyObject) {
if fractSwitchValue.on == true {
var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
var newSetting = NSEntityDescription.insertNewObjectForEntityForName("Settings", inManagedObjectContext: context) as NSManagedObject
newSetting.setValue(true, forKey: "fractionOnOff")
context.save(nil)
//println(newSetting)
}
else {
var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
var newSetting = NSEntityDescription.insertNewObjectForEntityForName("Settings", inManagedObjectContext: context) as NSManagedObject
newSetting.setValue(false, forKey: "fractionOnOff")
context.save(nil)
//println(newSetting)
}
}
}

Answer 1

I just did your example with CoreData. I just happened to store an NSString instead of a Bool. It's not optimized, but it should get you going.
import UIKit
import CoreData
class ViewController: UIViewController {
var state: NSString = ""
#IBOutlet weak var fractSwitchValue: UISwitch!
#IBAction func fractSwitch(sender: AnyObject) {
if fractSwitchValue.on == true {
state = "On"
save(state)
}
else {
state = "Off"
save(state)
}
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
var appDel = UIApplication.sharedApplication().delegate as AppDelegate
var context = appDel.managedObjectContext!
var request = NSFetchRequest(entityName: "Settings")
var error: NSError?
var results = context.executeFetchRequest(request, error: &error) as [NSManagedObject]?
if let fetchedResults = results {
state = fetchedResults[fetchedResults.count - 1].valueForKey("fractionOnOff") as String!
} else {
println("Could not fetch \(error), \(error!.userInfo)")
}
if state == "On" {
fractSwitchValue.setOn(true, animated: true)
} else {
fractSwitchValue.setOn(false, animated: true)
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
func save(string: NSString) {
let appDel = UIApplication.sharedApplication().delegate as AppDelegate
let context = appDel.managedObjectContext!
let entity = NSEntityDescription.entityForName("Settings", inManagedObjectContext: context)
let setting = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: context)
setting.setValue(string, forKey: "fractionOnOff")
println(string)
var error: NSError?
if !context.save(&error) {
println("Could not save \(error), \(error?.userInfo)")
}
}
}

Answer 2

I would use NSUserDefaults for this case. It's much easier to use than Core Data when storing user preferences. For example, you would store the property using
NSUserDefaults.standardUserDefaults().setBool(value, forKey: "fractionPreference")
and retrieve it using
let value = NSUserDefaults.standardUserDefaults().boolForKey("fractionPreference")