UIPickerView won't show the data loaded from NSUserDefaults

Question

EDIT:

I tried to set up NSUserDefaults last night but an error keeps occurring:

ViewController3:

save data

 @IBAction func addButtonTapped(sender: UIButton) {
    var userDefaults:NSUserDefaults = NSUserDefaults.standardUserDefaults()

    var itemList:NSMutableArray? = userDefaults.objectForKey("exercisesList") as? NSMutableArray

    var dataSet:NSMutableDictionary = NSMutableDictionary()
    dataSet.setObject(textField.text, forKey: "exercises")

    if ((itemList) != nil){ 
        var newMutableList:NSMutableArray = NSMutableArray();

        for dict:AnyObject in itemList!{
            newMutableList.addObject(dict as NSDictionary)
        }

        userDefaults.removeObjectForKey("exercisesList")
        newMutableList.addObject(dataSet)
        userDefaults.setObject(newMutableList, forKey: "exercisesList")

    }else{ 
        userDefaults.removeObjectForKey("exercisesList")
        itemList = NSMutableArray()
        itemList!.addObject(dataSet)
        userDefaults.setObject(itemList, forKey: "exercisesList")
    }

    userDefaults.synchronize()

    self.view.endEditing(true)
    textField.text = ""

}

ViewController1:

load data

 var exercises:NSMutableArray = NSMutableArray();


override func viewDidAppear(animated: Bool) {
    var userDefaults:NSUserDefaults = NSUserDefaults.standardUserDefaults()

    var itemListFromUserDefaults:NSMutableArray? = userDefaults.objectForKey("itemList") as? NSMutableArray

    if ((itemListFromUserDefaults) != nil){
        exercises = itemListFromUserDefaults!
    }
}

Now I wanted to use the loaded data for UIPickerView

 func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    switch pickerView {
    case pickerView1:
        return exercises[row] as String
    case pickerView2:
        return reps[component][row]
    case pickerView3:
        return weight[component][row]
    default:
        assertionFailure("Unknown pickerView")
    }
}

But at the point where the UIPickerView should return the exercises it is empty. Need some help here.

"How to store the added exercises" - store for how long? For later in the same run of the app? For later even after the app has been terminated? I mean, `var exercises` _is_ storage, so in what sense is the problem not already solved? — matt, Jan 22 '15 at 20:22
... have a look at http://stackoverflow.com/questions/24246749/whats-the-equivalent-of-nsarrays-writetofile-atomically-in-swift-and-array. — Martin R, Jan 22 '15 at 20:29
@matt : take a look at my edit please. information should be stored in the app after closing the app until the user removes it. — santa1, Jan 22 '15 at 20:32

zaph · Answer 1 · 2015-01-22T20:27:58.680

0

Don't use NSUserDefaults to pass variables.

Add a public property (in the .h file) to destinationViewController and set that property with the value (the array) in prepareForSegue.

To save the array between app launches do as @Martin suggests, writing the array to the Documents directory.There are many answers here with that information.

edited Jan 22 '15 at 20:27

answered Jan 22 '15 at 20:22

zaph

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Save it in coreData if you want to use it even after application is closed – NSSakly Jan 22 '15 at 20:25
1

@NSSakly : Can you give an example please? – santa1 Jan 22 '15 at 20:29
4

Do NOT use core data. It is not a beginner tool. – matt Jan 22 '15 at 20:43
i confirm, i just see your edit description that you are beginner. No solution for that, just user NSUserDefault – NSSakly Jan 22 '15 at 20:44
I tried as suggested but I'm not quite sure if its working because an error keeps occurring. Please take a look at my edited question. Thank you – santa1 Jan 24 '15 at 10:18

Leo Dabus · Answer 2 · 2015-01-22T21:19:19.307

How to store your arrays using NSUserDefaults is pretty simple and I encourage you to try it.

var exercises = ["A","B","C"]
NSUserDefaults.standardUserDefaults().setObject(exercises, forKey: "exercises")

How to load your string arrays using NSUserDefaults

if let myLoadedStringArray = NSUserDefaults.standardUserDefaults().stringArrayForKey("exercises"){
    println(myLoadedStringArray)   // "[A, B, C]"
}
// Note: myLoadedStringArray has no value outside curly brackets

How to delete/reset a value stored using NSUserDefaults

NSUserDefaults.standardUserDefaults().removeObjectForKey("exercises")

println(NSUserDefaults.standardUserDefaults().stringArrayForKey("exercises"))    // "nil"

If you prefer to store it as a file at the documents folder you can do as follow

let fileUrl = (NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first! as NSURL).URLByAppendingPathComponent("exercises.db")
(exercises as NSArray).writeToURL(fileUrl, atomically: true)  // true
// forced unwrap if you are sure it won't return nil
let loadedArray = NSArray(contentsOfURL: fileUrl)! as [String]
// or use if let to safely unwrap your array
if let loadedArray = NSArray(contentsOfURL: fileUrl) as? [String] {
    println(loadedArray)  // "[A, B, C]"
}

I tried as you suggested but I'm not quite sure if its working because an error keeps occurring. Please take a look at my edited question. Thank you! — santa1, Jan 24 '15 at 10:18

ljk321 · Accepted Answer · 2015-01-25T10:22:56.353

0

I think I've got this.

In your code, you read exercises from UserDefaults in viewDidAppear, which will be called after func pickerView(...) -> String! is called. That's why in func pickerView(...) -> String! the exercises is always empty.

To do this correctly, you need to initialize exercises in init() or viewDidLoad()

edited Jan 25 '15 at 10:22

answered Jan 25 '15 at 08:26

ljk321

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So what other options do I have? I know I could write viewDidLoad (if that would change anything) but this would mean, that the data will only be loaded once. – santa1 Jan 25 '15 at 10:31
@santa1 You could also write it within `func pickerView()->String`. It will be "slower", but surely acceptable. With more optimization(caching or something), the performance shouldn't be a problem. – ljk321 Jan 25 '15 at 10:35
And whats about reloading the data of the picker view within the func of the NSUserDefault? Would that be possible? – santa1 Jan 25 '15 at 10:40
EDIT: I have tried as you suggested but something else seems to be wrong. Just can't figure out what. – santa1 Jan 25 '15 at 10:52
@santa1 I'm guessing there are more than one picker view, and they need to change dynamiclly. If something can trigger the change, would it be ok to just use `pickerView.reloadAllComponents` ? – ljk321 Jan 25 '15 at 11:06
Yes there are more but only one should use the date from NSUserDefaults. I'll try. – santa1 Jan 25 '15 at 17:35

UIPickerView won't show the data loaded from NSUserDefaults

3 Answers3