CODEWITHSUNDEEP
iosxcodeswiftxcode6
Atharva Vaidya
Atharva Vaidya

Reputation: 764

How to retrieve and assign a NSDate object from NSUserDefaults?

I am building a stopwatch application and I need to store the start date before the user closes the application and need to retrieve it when the user opens the application again.

So for example if the user starts the stopwatch and then closes the application and then after some time opens the application again the app should add the time between the opening and closing to the running time if the stopwatch was running.

I have created two functions in my viewcontroller that handle this. Here's the code:

    override func viewWillAppear(animated: Bool)
    {

      let startTimedefault:NSUserDefaults = NSUserDefaults.standardUserDefaults()

      let startTimesaved:NSDate = startTimedefault.objectForKey("start time") // This line is buggy


      if(launchBool == true)
      {      
         timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "fireStopWatch", userInfo: nil, repeats: true)

         startTime = startTimesaved
      }

      if(launchBool == false)
      {
         timer.invalidate()
      }

    }

    override func viewWillDisappear(animated: Bool)
    {
       NSUserDefaults.standardUserDefaults().setObject(launchBool, forKey: "Start/Stop")
       NSUserDefaults.standardUserDefaults().setObject(startTime, forKey: "start time")
       NSUserDefaults.standardUserDefaults().setObject(elapsedTime, forKey: "elapsed time")
    }

I have gone through a couple of posts here on StackOverflow :

What's the optimum way of storing an NSDate in NSUserDefaults?

iOS - Not able to store NSDate into NSUserDefaults

Upvotes: 43

Views: 22263

Answers (3)

KlimczakM
KlimczakM

Reputation: 12914

Swift 3/4/5 version using Date (type alias) instead of NSDate:

let yourDate = UserDefaults.standard.object(forKey: "yourKey") as? Date
UserDefaults.standard.set(yourDate, forKey: "yourKey")

Remember to use conditional cast operator as? to avoid crash if there is no date yet under "yourKey" in UserDefaults.

Upvotes: 34

dengST30
dengST30

Reputation: 4037

In Swift 5,

You can do some easy encapsulation for better managing the code

struct UserSetting {

    static var shared = UserSetting()

    var practiceTime: Date?{
        get {
            return UserDefaults.standard.object(forKey: TimeScaler.start) as? Date
        }
        set(newVal){
            UserDefaults.standard.set(newVal, forKey: TimeScaler.start)
        }
    }

}



struct TimeScaler {

    static let start = "start"
}

Upvotes: 3

Sujith Thankachan
Sujith Thankachan

Reputation: 3506

Set your date object as follows:

UserDefaults.standard.set(Date(), forKey:"yourKey")

Retrieve it using:

UserDefaults.standard.object(forKey: "yourKey") as? Date

Date will be optional of course, because it might never have been set.

Upvotes: 106

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