iosswiftnsuserdefaultsuserdefaults

How can I use UserDefaults in Swift?


How can I use UserDefaults to save/retrieve strings, booleans and other data in Swift?


Solution

  • ref: NSUserdefault objectTypes

    Swift 3 and above

    Store

    UserDefaults.standard.set(true, forKey: "Key") //Bool
    UserDefaults.standard.set(1, forKey: "Key")  //Integer
    UserDefaults.standard.set("TEST", forKey: "Key") //setObject
    

    Retrieve

     UserDefaults.standard.bool(forKey: "Key")
     UserDefaults.standard.integer(forKey: "Key")
     UserDefaults.standard.string(forKey: "Key")
    

    Remove

     UserDefaults.standard.removeObject(forKey: "Key")
    

    Remove all Keys

     if let appDomain = Bundle.main.bundleIdentifier {
    UserDefaults.standard.removePersistentDomain(forName: appDomain)
     }
    

    Swift 2 and below

    Store

    NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "yourkey")
    NSUserDefaults.standardUserDefaults().synchronize()
    

    Retrieve

      var returnValue: [NSString]? = NSUserDefaults.standardUserDefaults().objectForKey("yourkey") as? [NSString]
    

    Remove

     NSUserDefaults.standardUserDefaults().removeObjectForKey("yourkey")
    


    Register

    registerDefaults: adds the registrationDictionary to the last item in every search list. This means that after NSUserDefaults has looked for a value in every other valid location, it will look in registered defaults, making them useful as a "fallback" value. Registered defaults are never stored between runs of an application, and are visible only to the application that registers them.

    Default values from Defaults Configuration Files will automatically be registered.

    for example detect the app from launch , create the struct for save launch

    struct DetectLaunch {
    static let keyforLaunch = "validateFirstlunch"
    static var isFirst: Bool {
        get {
            return UserDefaults.standard.bool(forKey: keyforLaunch)
        }
        set {
            UserDefaults.standard.set(newValue, forKey: keyforLaunch)
        }
    }
    }
    

    Register default values on app launch:

    UserDefaults.standard.register(defaults: [
            DetectLaunch.isFirst: true
        ])
    

    remove the value on app termination:

    func applicationWillTerminate(_ application: UIApplication) {
        DetectLaunch.isFirst = false
    
    }
    

    and check the condition as

    if DetectLaunch.isFirst {
      // app launched from first
    }
    

    UserDefaults suite name

    another one property suite name, mostly its used for App Groups concept, the example scenario I taken from here :

    The use case is that I want to separate my UserDefaults (different business logic may require Userdefaults to be grouped separately) by an identifier just like Android's SharedPreferences. For example, when a user in my app clicks on logout button, I would want to clear his account related defaults but not location of the the device.

    let user = UserDefaults(suiteName:"User")
    

    use of userDefaults synchronize, the detail info has added in the duplicate answer.