ios - Swift NSUserDefaults not saving Dictionary -

here code. have been solving bug month still not solved.

here codes.

 var color : string = ""  var colorsentdictionary = dictionary<string, int>()   override func viewwillappear(animated: bool) {     super.viewwillappear(animated)      // load colorsentdictionary     self.loadcolorsentdictionary()  }   func loadcolorsentdictionary () {      // load total messages sent     var defaults : nsuserdefaults = nsuserdefaults.standarduserdefaults()     if (defaults.dictionaryforkey("colorsentdictionary") != nil) {         var colorsentdictionary : nsdictionary = defaults.dictionaryforkey("colorsentdictionary")!         self.colorsentdictionary = colorsentdictionary dictionary     } }  func savecolorsentdictionary () {      // save total messages received     var defaults : nsuserdefaults = nsuserdefaults.standarduserdefaults()     var colorsentdictionary : nsdictionary = self.colorsentdictionary     defaults.setobject(colorsentdictionary, forkey: "colorsentdictionary")     defaults.synchronize()       if (defaults.dictionaryforkey("colorsentdictionary") != nil) {         println("it not nil !!!!!!!!!") } else { println("it nil") } }   @ibaction func sendmessage(sender : anyobject) {  self.color = "yellow"  println("the color of message is: \(self.color)")      // add value messagesentdictionary     if (self.colorsentdictionary["\(self.color)"] != nil) {         var colorsentcount : int = self.colorsentdictionary[self.color]!         self.colorsentdictionary["\(self.color)"] = colorsentcount+1         println("it exists")     } else {         self.colorsentdictionary["\(self.color)"] = 1         println("not exist")     }      self.savecolorsentdictionary()      self.navigationcontroller!.poptorootviewcontrolleranimated(true) } 

whenever trigger save method, colorsentdictionary not saved. log prints "it nil" cannot find key "colorsentdictionary".

but if put self.savecolorsentdictionary () in viewwillappear, dictionary saved , log prints "it not nil !!!!!!!!".

i think problem weird don't think bug since tested in official release version of xcode 6. can please solve me? :)