ios - NSKeyedUnarchiver returns nil - Could not cast value of type 'MyProj.Meal' (0x105373f68) to 'MyProj.Meal' (0x11f5ee928) -

i'm trying hang of archiving objects. i'm following apple's example project persistence here: https://developer.apple.com/library/content/referencelibrary/gettingstarted/developiosappsswift/persistdata.html

basically there's meal class conforms nscoding protocol. when run tests archive/unarchive meal object, following error:

could not cast value of type 'myproj.meal' (0x105373f68) 'myproj.meal' (0x11f5ee928) 

here's code produces error; error on third line:

let meal = meal(name: "food", photo: nil, rating: 4)! let data = nskeyedarchiver.archiveddata(withrootobject: meal) let unarchivedmeal = nskeyedunarchiver.unarchiveobject(with: data) as! meal  xctassertnotnil(unarchivedmeal) 

and here's meal class apple:

// //  meal.swift //  foodtracker // //  created jane appleseed on 11/10/16. //  copyright © 2016 apple inc. rights reserved. //  import uikit import os.log  class meal: nsobject, nscoding {  //mark: properties  var name: string var photo: uiimage? var rating: int  //mark: archiving paths static let documentsdirectory = filemanager().urls(for: .documentdirectory, in: .userdomainmask).first! static let archiveurl = documentsdirectory.appendingpathcomponent("meals")  //mark: types  struct propertykey {     static let name = "name"     static let photo = "photo"     static let rating = "rating" }  //mark: initialization  init?(name: string, photo: uiimage?, rating: int) {      // name must not empty     guard !name.isempty else {         return nil     }      // rating must between 0 , 5 inclusively     guard (rating >= 0) && (rating <= 5) else {         return nil     }      // initialization should fail if there no name or if rating negative.     if name.isempty || rating < 0  {         return nil     }      // initialize stored properties.     self.name = name     self.photo = photo     self.rating = rating  }  //mark: nscoding  func encode(with acoder: nscoder) {     acoder.encode(name, forkey: propertykey.name)     acoder.encode(photo, forkey: propertykey.photo)     acoder.encode(rating, forkey: propertykey.rating) }  required convenience init?(coder adecoder: nscoder) {      // name required. if cannot decode name string, initializer should fail.     guard let name = adecoder.decodeobject(forkey: propertykey.name) as? string else {         debugprint("unable decode name meal object.")         return nil     }      // because photo optional property of meal, use conditional cast.     let photo = adecoder.decodeobject(forkey: propertykey.photo) as? uiimage      let rating = adecoder.decodeinteger(forkey: propertykey.rating)      // must call designated initializer.     self.init(name: name, photo: photo, rating: rating)      } } 

any ideas? frustrating