Access a Dictionary index saved in Swift session

Question

So I basically have a login screen on my app and after a successful login, before performing a segue to the main screen I save the following info in a Dictionary in session. It's something like this (putting static info for the example):

    let preferences = UserDefaults.standard
    let session_info : [String: String] = [
        "user_id": "123",
        "name": "John",
        "email": "[email protected]"
    ]
    preferences.set(session_info, forKey: "session")
    preferences.synchronize()

So the session data gets saved, if I assign it to a variable and print it, I get an optional dictionary of info in my console.

    let session_data = preferences.value(forKey: "session")!

If I do a print(session_data) I get this output:

   {
       "user_id" = "123";
       "name" = "John";
       "email" = "[email protected]";
   }

My issue is that I am not sure how to access the keys, because if I treat the assigned variable as a Dictionary it says Type 'Any' has no subscript members. What I use is this:

   print(session_data["user_id"])

Is there a way to access this info or do I have to save each variable to a separate session key?

Answer 1

Basically never use value(forKey with UserDefaults.

There is a dedicated API dictionary(forKey which returns [String:Any]? by default. In your case conditionally downcast the dictionary to [String:String].

if let sessionData = preferences.dictionary(forKey: "session") as? [String:String] {
   print(sessionData["user_id"]!)
} else {
   print("sessionData is not available")
}

And this is not JavaScript. Please name variables lowerCamelCased.

---

A more sophisticated way is to use a struct and save it with Codable

struct Session : Codable {
    let userID, name, email : String
}

let preferences = UserDefaults.standard
let sessionInfo = Session(userID:"123", name: "John", email: "[email protected]")
let sessionData = try! JSONEncoder().encode(sessionInfo)
preferences.set(sessionData, forKey: "session")

---

do {
    if let sessionData = preferences.data(forKey: "session") {
        let sessionInfo = try JSONDecoder().decode(Session.self, from: sessionData)
        print(sessionInfo.userID)
    }
} catch { print(error) }

Answer 2

You have to parse it as a Dictionary.

guard let session_data = preferences.value(forKey: "session")! as? NSDictionary else {return }
print(session_data["user_id"])

It should works.