Swift NSUserDefaults not saving Dictionary?

Question

I have the following test code:

  func testSaveDictionary() {     let userDefaults = NSUserDefaults.standardUserDefaults()     var jo = [       "a" : "1.0",       "b" : "2.0"     ]      let akey = "aKey"     userDefaults.setObject(jo, forKey: akey)     var isOk = userDefaults.synchronize()      var data0 = userDefaults.dictionaryForKey(akey)     println(data0)    } 

The output of println(data0) is nil.

Anything wrong with my code? Is Swift Dictionary considered property list now or in the final release?

Answer 1

Update for Swift 2, Xcode 7: As @atxe noticed, NSUserDefaults dictionaries are now mapped as [String, AnyObject]. This is a consequence of the Objective-C "lightweight generics" which allow to declare the Objective-C method as

- (NSDictionary<NSString *,id> *)dictionaryForKey:(NSString *)defaultName 

(Default objects must be property lists and in particular the dictionary keys can only be strings.)

On the other hand, a Swift dictionary is bridged automatically if possible, so the original code from the question works (again):

let jo = [     "a" : "1.0",     "b" : "2.0" ]  let akey = "aKey" // Swift 2: userDefaults.setObject(jo, forKey: akey) // Swift 3: userDefaults.set(jo, forKey: akey) 

---

Original answer for Swift 1.2: The user defaults can store NSDictionary objects. These are mapped to Swift as [NSObject : AnyObject]:

var jo : [NSObject : AnyObject] = [     "a" : "1.0",     "b" : "2.0" ]  userDefaults.setObject(jo, forKey: akey) var isOk = userDefaults.synchronize() 

And note that dictionaryForKey() returns an optional, so you should check it for example with an optional assignment:

if let data0 = userDefaults.dictionaryForKey(akey) {     print(data0) } else {     print("not set") }  // Output: [b: 2.0, a: 1.0] 

Answer 2

You need to convert it into NSData first. Something like this:

var data = NSKeyedArchiver.archivedDataWithRootObject(jo) var userDefaults = NSUserDefaults.standardUserDefaults() userDefaults.setObject(data, forKey:akey)