swift - iOS App Delegate Crash -

i receiving error after app delegate crashes.

2016-11-17 10:01:34.780 foodie[38429:3212774] * terminating app due uncaught exception 'nsinvalidunarchiveoperationexception', reason: '* -[nskeyedunarchiver decodeobjectforkey:]: cannot decode object of class (photomania.item) key (ns.objects); class may defined in source code or library not linked'

how can fix it?

here app delegate:

@uiapplicationmain class appdelegate: uiresponder, uiapplicationdelegate {  var window: uiwindow?  // override point customization after application launch.  //create imagestore //let imagestore = imagestore() //let itemstore = itemstore()  //access itemsviewcontroller , set item store //let navcontroller = window!.rootviewcontroller as! uinavigationcontroller //let itemscontroller = navcontroller.topviewcontroller as! itemsviewcontroller  //itemscontroller.itemstore = itemstore //itemscontroller.imagestore = imagestore  func application(application: uiapplication, didfinishlaunchingwithoptions launchoptions: [nsobject: anyobject]?) -> bool {      let rootcontroller = window?.rootviewcontroller      if rootcontroller uitabbarcontroller {         let firsttabitem = (rootcontroller as! uitabbarcontroller).viewcontrollers?[0]          if firsttabitem uinavigationcontroller {              let firstcontroller = (firsttabitem as! uinavigationcontroller).viewcontrollers.first as! itemsviewcontroller             firstcontroller.itemstore  = itemstore()             firstcontroller.imagestore = imagestore()         }     }     return true }  func applicationwillresignactive(application: uiapplication) { }  func applicationwillenterforeground(application: uiapplication) { }  func applicationdidbecomeactive(application: uiapplication) { }  func applicationwillterminate(application: uiapplication) { }  func applicationdidenterbackground(application: uiapplication) {  } } 

here photomania.item.swift :

     import uikit      class item: nsobject, nscoding {        var meal: string        var restaurantname: string?        var valueindollars: int        let datecreated: nsdate        let itemkey: string  func encodewithcoder(acoder: nscoder) {     acoder.encodeobject(meal, forkey: "meal")     acoder.encodeobject(datecreated, forkey: "datecreated")     acoder.encodeobject(itemkey, forkey: "itemkey")     acoder.encodeobject(restaurantname, forkey: "restaurantname")      acoder.encodeinteger(valueindollars, forkey: "valueindollars") }  required init(coder adecoder: nscoder) {     meal = adecoder.decodeobjectforkey("meal") as! string     datecreated = adecoder.decodeobjectforkey("datecreated") as! nsdate     itemkey = adecoder.decodeobjectforkey("itemkey") as! string     restaurantname = adecoder.decodeobjectforkey("restaurantname") as! string?      valueindollars = adecoder.decodeintegerforkey("valueindollars")      super.init()  }  init(meal: string, restaurantname: string, valueindollars: int) {     self.meal = meal     self.restaurantname = restaurantname     self.valueindollars = valueindollars     self.datecreated = nsdate()     self.itemkey = nsuuid().uuidstring      super.init()  }  convenience init(random: bool = false) {     self.init(meal: "meal", restaurantname: "restaurant", valueindollars: 0)  } } 

item store:

import uikit  class itemstore {  var allitems = [item]()  let itemarchiveurl: nsurl = {     let documentsdirectories =         nsfilemanager.defaultmanager().urlsfordirectory(.documentdirectory, indomains:  .userdomainmask)     let documentdirectory = documentsdirectories.first!     return documentdirectory.urlbyappendingpathcomponent("items.archive") } ()  func createitem() -> item {     let newitem = item(random: true)      allitems.append(newitem)      return newitem }  func removeitem(item: item) {     if let index = allitems.indexof(item) {         allitems.removeatindex(index)     } } func moveitematindex(fromindex: int, toindex: int) {     if fromindex == toindex {         return     }     let moveditem = allitems[fromindex]     allitems.removeatindex(fromindex)     allitems.insert(moveditem, atindex: toindex) } func savechanges() -> bool {     print("saving items to: \(itemarchiveurl.path!)")     return nskeyedarchiver.archiverootobject(allitems, tofile: itemarchiveurl.path!) } init() {     if let archiveditems =         nskeyedunarchiver.unarchiveobjectwithfile(itemarchiveurl.path!) as? [item] {             allitems += archiveditems     } } func imageurlforkey(key: string) -> nsurl {     let documentsdirectories = nsfilemanager.defaultmanager().urlsfordirectory(.documentdirectory, indomains: .userdomainmask)     let documentdirectory = documentsdirectories.first!      return documentdirectory.urlbyappendingpathcomponent(key)  } }