Saving custom NSObject in NSUserDefaults - ios

Question

I'm having a modal entity file as below,
import UIKit
class MyProfile: NSObject {
var userName : String = ""
func initWithDict(dict: NSMutableDictionary) {
self.userName = dict.objectForKey("username") as! String
}
}
Saving that entity by encoding as below,
let myDict: NSMutableDictionary = ["username": "abc"]
let myEntity:MyProfile = MyProfile()
myEntity.initWithDict(myDict)
let userDefaults = NSUserDefaults.standardUserDefaults()
let encodedData = NSKeyedArchiver.archivedDataWithRootObject(myEntity)
userDefaults.setObject(encodedData, forKey: "MyProfileEntity")
userDefaults.synchronize()
Getting that saved entity as below,
let myEntity:MyProfile = MyProfile()
let userDefaults = NSUserDefaults.standardUserDefaults()
guard let decodedNSData = userDefaults.objectForKey("MyProfileEntity") as? NSData,
myEntity = NSKeyedUnarchiver.unarchiveObjectWithData(decodedNSData) as? MyProfile!
else {
print("Failed")
return
}
print(myEntity.userName)
It's not working, having crashes and lot of syntax errors, I'm new to swift,
It's showing some syntax errors like definition conflicts with previous value in the unarchiveObjectWithData line. If I fix that error, then at the time of getting the entity from userdefaults it's crashing.
can anyone suggest how can I resolve it?

Answer 1

To save custom object into user default, you must implement NSCoding protocol. Please replace your custom data model like this:
class MyProfile: NSObject,NSCoding {
var userName : String = ""
#objc required init(coder aDecoder:NSCoder){
self.userName = aDecoder.decodeObjectForKey("USER_NAME") as! String
}
#objc func encodeWithCoder(aCoder: NSCoder) {
aCoder.encodeObject(self.userName, forKey: "USER_NAME")
}
init(dict: [String: String]) {
self.userName = dict["username"]!
}
override init() {
super.init()
}
}
Here is the code for saving and retrieving MyProfile object:
// Save profile
func saveProfile(profile: MyProfile){
let filename = NSHomeDirectory().stringByAppendingString("/Documents/profile.bin")
let data = NSKeyedArchiver.archivedDataWithRootObject(profile)
data.writeToFile(filename, atomically: true)
}
// Get profile
func getProfile() -> MyProfile?{
if let data = NSData(contentsOfFile: NSHomeDirectory().stringByAppendingString("/Documents/profile.bin")){
let unarchiveProfile = NSKeyedUnarchiver.unarchiveObjectWithData(data) as! MyProfile
return unarchiveProfile
} else{
return nil
}
}
Now here is the code snippet how to use those method:
// Create profile object
let profile = MyProfile(dict: ["username" : "MOHAMMAD"])
// save profile
saveProfile(profile)
// retrieve profile
if let myProfile = getProfile(){
print(myProfile.userName)
}else{
print("Profile not found")
}

Answer 2

You can't do this:
let myEntity:MyProfile = MyProfile()
Then later on, do this:
myEntity = ...
When something is defined with 'let', you cannot change it.
Change to
var myEntity: MyProfile?
It is possible that
NSKeyedUnarchiver.unarchiveObjectWithData(decodedNSData)
is returning nil. You then proceed to force unwrapping by adding
as? MyProfile!
try changing this to
as? MyProfile
Then later, see if you got something back
if let myEntity = myEntity {
print(myEntity.userName)
}