Conforming Class to NSCoding - ios

Question

I conformed my following Person class to NSCoding protocol.
class Person: NSObject, NSCoding{
var age:Int
var height: Double
var name: String
init(age:Int, height: Double, name:String){
self.age = age
self.height = height
self.name = name
}
func encode(with aCoder: NSCoder){
aCoder.encode(age, forKey: "age")
aCoder.encode(height, forKey: "height")
aCoder.encode(name, forKey: "name")
}
required init?(coder aDecoder: NSCoder){
age = aDecoder.decodeObject(forKey: "age") as! Int **//error**
height = aDecoder.decodeObject(forKey: "height") as! Double
name = aDecoder.decodeObject(forKey: "name") as! String
super.init()
}
}
Then, I created an array of this class. I archived it to a plist using NSKeyedArchiver and everything was fine. However, when I tried to unarchive it I got an error involving unwrapping a optional which was nil. The error showed up in the Person class where marked. This is the code I used:
if let people = unarchive(){
print(people)
}
Here's the function for unarchiving:
func unarchive()->[Person]?{
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let documentDirectory = paths[0]
let path = documentDirectory.appending("ObjectData.plist")
let fileManager = FileManager.default
if(!fileManager.fileExists(atPath: path)){
if let bundlePath = Bundle.main.path(forResource: "ObjectData", ofType: "plist"){
do{
try fileManager.copyItem(atPath: bundlePath, toPath: path)
}catch{
print("problem copying")
}
}
}
if let objects = NSKeyedUnarchiver.unarchiveObject(withFile: path){
if let people = objects as? [Person]{
return people
}else{
return nil
}
}else{
return nil
}
}

Answer 1

Int and Double are not archived as objects. aDecoder.decodeObject(forKey: <key>) for them will always return nil, and using as! with nil will crash your app.
So, instead use this:
aDecoder.decodeInteger(forKey: "age")
aDecoder.decodeDouble(forKey: "height")
For name field you may keep your code.

Answer 2

You should use the proper decoding methods for Int and Double. You could paste the following code in a playground and test it :
import Foundation
class Person: NSObject, NSCoding{
var age:Int
var height: Double
var name: String
init(age:Int, height: Double, name:String){
self.age = age
self.height = height
self.name = name
}
func encode(with aCoder: NSCoder) {
aCoder.encode(age, forKey: "age")
aCoder.encode(height, forKey: "height")
aCoder.encode(name, forKey: "name")
}
required init?(coder aDecoder: NSCoder) {
age = aDecoder.decodeInteger(forKey: "age")
height = aDecoder.decodeDouble(forKey: "height")
name = aDecoder.decodeObject(forKey: "name") as! String
super.init()
}
}
let john = Person(age: 30, height: 170, name: "John")
let mary = Person(age: 25, height: 140, name: "Mary")
let guys = [john, mary]
let data = NSKeyedArchiver.archivedData(withRootObject: guys)
let people = NSKeyedUnarchiver.unarchiveObject(with: data)
dump (people)