How can I store a Swift enum value in NSUserDefaults

Question

I have an enum like this:

enum Environment {     case Production     case Staging     case Dev } 

And I'd like to save an instance in NSUserDefaults like this:

func saveEnvironment(environment : Environment){     NSUserDefaults.standardUserDefaults().setObject(environment, forKey: kSavedEnvironmentDefaultsKey) } 

I understand that a Swift enum isn't an NSObject, and that makes it difficult to save, but I'm unsure what the best way is to convert it to something storable.

Answer 1

Using rawValue for the enum is one way of using types that can be stored in NSUserDefaults, define your enum to use a rawValue. Raw values can be strings, characters, or any of the integer or floating-point number types :

enum Environment: String {     case Production = "Prod"     case Staging    = "Stg"     case Dev        = "Dev" } 

You can also create an enum instance directly using the rawValue (which could come from NSUserDefaults) like:

let env = Environment(rawValue: "Dev") 

You can extract the rawValue (String) from the enum object like this and then store it in NSUserDefaults if needed:

if let myEnv = env {     println(myEnv.rawValue) }   func saveEnvironment(environment : Environment){     NSUserDefaults.standardUserDefaults().setObject(environment.rawValue, forKey: kSavedEnvironmentDefaultsKey) } 

Answer 2

If you would like to save/read data from UserDefaults and separate some logic, you can do it in following way (Swift 3):

enum Environment: String {     case Production     case Staging     case Dev }  class UserDefaultsManager {      static let shared = UserDefaultsManager()      var environment: Environment? {        get {            guard let environment = UserDefaults.standard.value(forKey: kSavedEnvironmentDefaultsKey) as? String else {                return nil            }            return Environment(rawValue: environment)        }        set(environment) {            UserDefaults.standard.set(environment?.rawValue, forKey: kSavedEnvironmentDefaultsKey)        }     } } 

So saving data in UserDefaults will look this way:

UserDefaultsManager.shared.environment = Environment.Production 

And reading data, saved in UserDefaults in this way:

if let environment = UserDefaultsManager.shared.environment {     //you can do some magic with this variable } else {     print("environment data not saved in UserDefaults") }