Store [String] in NSUserDefaults

Question

I want to save a Swift Style String Array into NSUserDefaults, but acutally the "if" statement in the code says that returnValue is always nil.

Later in the code (iOS 8) I want to use "food += ["spaghetti"] to add new entries.

var food : [String] {
    get {
        var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
        if returnValue == nil      //Check for first run of app
        {
            returnValue = ["muesli", "banana"]; //Default value
        }
        return returnValue!
    }
    set (newValue) {
        NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
        NSUserDefaults.standardUserDefaults().synchronize()
    }
}

i was also trying several things from this [link](http://stackoverflow.com/questions/24032863/swift-and-nsuserdefaults-exc-bad-instruction-when-user-defaults-empty) but it didn't bring up the solution — Thomas, Aug 21 '14 at 07:52
it seems your problem is you never save those values into the user defaults, because adding a new item to the array does not call the setter. you need to set the actual `food` directly somewhere (e.g. `food = ["such", "and", "such"]`) to get it saved. — holex, Aug 21 '14 at 08:56
I just tried your code in latest Xcode7 and Swift2.0, and it's actually perfect. — LiangWang, Jun 17 '15 at 13:31
This is best example for NSUserDefault : http://iosdevcenters.blogspot.com/2016/05/save-data-using-nsuserdefaults-in-swift.html — Chetan Prajapati, May 23 '16 at 06:18

Imanou Petit · Accepted Answer · 2016-01-05T23:09:48.283

The following code should help you resolve your problem:

import UIKit

class ViewController: UIViewController {

    var food: [String] {
        get {
            if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
                return returnValue
            } else {
                return ["muesli", "banana"] //Default value
            }
        }
        set {
            NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
            NSUserDefaults.standardUserDefaults().synchronize()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        print(food) // prints: ["muesli", "banana"] (at first launch)

        food = ["cake"]
        print(food) // prints: ["cake"]

        food += ["spaghetti"]
        print(food) // prints: ["cake", "spaghetti"]

        food = []
        print(food) // prints: []

        NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
        print(food) // prints: ["muesli", "banana"]
    }

}

However, with the previous code, if you set food = [], you will have a problem as food won't return ["muesli", "banana"]. In order to avoid this, you may prefer the following code:

import UIKit

class ViewController: UIViewController {

    var food: [String] {
        get {
            if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
                return returnValue == [] ? ["muesli", "banana"] : returnValue
            } else {
                return ["muesli", "banana"] //Default value
            }
        }
        set {
            NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
            NSUserDefaults.standardUserDefaults().synchronize()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        print(food) // prints: ["muesli", "banana"] (at first launch)

        food = ["cake"]
        print(food) // prints: ["cake"]

        food += ["spaghetti"]
        print(food) // prints: ["cake", "spaghetti"]

        food = []
        print(food) // prints: ["muesli", "banana"]

        NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
        print(food) // prints: ["muesli", "banana"]
    }

}

Curious, why would you declare food as [NSString] instead of [String]? You can convert to [NSString] for storage in NSUserDefaults, then return [String] when returning from NSUserDefaults. — Dylan, Apr 13 '15 at 00:14

pNre · Answer 2 · 2014-08-21T09:18:16.590

As stated in the documentation:

For NSArray and NSDictionary objects, their contents must be property list objects.

This means you need to convert your String objects to NSString when saving, something like this should work:

var food : [String] {
    get {
        var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
        if returnValue == nil      //Check for first run of app
        {
            returnValue = ["muesli", "banana"]; //Default value
        }
        return returnValue!
    }
    set (newValue) {
        //  Each item in newValue is now a NSString
        let val = newValue as [NSString]
        NSUserDefaults.standardUserDefaults().setObject(val, forKey: "food")
        NSUserDefaults.standardUserDefaults().synchronize()
    }
}

Seems like this is best since you're only converting to [NSString] for storage, while returning [String] from storage. — Dylan, Apr 13 '15 at 00:06

Sina · Answer 3 · 2016-12-10T09:02:55.347

9

In Swift 3.0

Store

UserDefaults.standard.set(newValue, forKey: "yourkey")
UserDefaults.standard.synchronize()

Retrieve

var returnValue: [NSString]? = UserDefaults.standard.object(forKey: "yourkey") as? [NSString]

Remove

UserDefaults.standard.removeObject(forKey: "yourkey")

Reference: NSUserdefault objectTypes

edited Dec 10 '16 at 09:02

answered Nov 05 '16 at 10:17

Sina

849
9
21

PSS · Answer 4 · 2016-04-20T11:28:48.090

Set and Get NSUserDefault with function

Use below function to globally use , declare in any class any use in whole app

Declaration

func setUserDefault(ObjectToSave : AnyObject?  , KeyToSave : String)
{
    let defaults = NSUserDefaults.standardUserDefaults()

    if (ObjectToSave != nil)
    {

        defaults.setObject(ObjectToSave, forKey: KeyToSave)
    }

    NSUserDefaults.standardUserDefaults().synchronize()
}

func getUserDefault(KeyToReturnValye : String) -> AnyObject?
{
    let defaults = NSUserDefaults.standardUserDefaults()

    if let name = defaults.valueForKey(KeyToReturnValye)
    {
        return name
    }
    return nil
}

How to call

Classname_where_this_function_declare.sharedInstance.setUserDefault("value", KeyToSave: "key")**

score -1 · Answer 5 · edited Mar 28 '18 at 08:29

//

    class func saveCustomObject(_ object: AnyObject?, key: String) { 
      let encodedObject = NSKeyedArchiver.archivedData(withRootObject: object!) 
      let userDefaults = UserDefaults.standard userDefaults.set(encodedObject, forKey: key) 
      userDefaults.synchronize() 
    }

//

class func loadCustomObject(_ key: String) -> AnyObject? { 
   let userDefaults = UserDefaults.standard 
   if let userDefaultKey = userDefaults.object(forKey: key) { 
     let encodedObject = userDefaultKey as! NSData 
     return NSKeyedUnarchiver.unarchiveObject(with: encodedObject as Data)! as AnyObject? 
   } else {
     return nil 
   }
}

//

class func removeCustomObject(_ key: String) { // 
    let encodedObject = NSKeyedArchiver.archivedDataWithRootObject(object!) let userDefaults = 
    UserDefaults.standard userDefaults.removeObject(forKey: key) 
    userDefaults.synchronize()
 }

call Method

let aParams : [String : String] = [ "DeviceType" : "iOS", ]
CommonMethods.saveCustomObject(aParams as AnyObject?, key:Constants.kLoginData)

Store [String] in NSUserDefaults

5 Answers5

How to call

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