UIPickerView won't show the data loaded from NSUserDefaults - ios

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.

Answer 1

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()

Answer 2

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.

Answer 3

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]"
}