Get minutes remaining between dates in Swift - swift

Question

My question is based on a time interval
I'm getting the hour and minutes (NOW) and I want to create a timer for 75 minutes since that moment but I want the timer to continue working even if i close the app even on multitasking
So i was thinking if I save the time as a NSUserDefault value and every time I open the app It reads the stored value and recalculates
This is my actual code
override func viewDidLoad() {
super.viewDidLoad()
var timer = NSTimer.scheduledTimerWithTimeInterval(30, target: self, selector: Selector("update"), userInfo: nil, repeats: true)
}
func update() {
//here I should update the GUI with the remaining minutes and do a NSUserDefault check if the 75 minutes have already
}
#IBAction func save_time(sender: AnyObject) {
let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components(.CalendarUnitHour | .CalendarUnitMinute, fromDate: date)
var hour = components.hour
var minutes = components.minute + 75
if (minutes>59){
hour += 1
minutes -= 60
}
defs.setInteger(hour, forKey: "u_hora")
defs.setInteger(minutes, forKey: "u_minutos")
}

Answer 1

You can just store them as TimeInterval using NSUserDefaults and you should create a time interval extension to format your time string as desired:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var strTimer: UILabel!
var tasksManager = NSTimer()
var endTime:NSTimeInterval = 0
var now: NSTimeInterval {
return NSDate().timeIntervalSinceReferenceDate
}
func updateTime(){
strTimer.text = ( endTime - now ).time
}
override func viewDidLoad() {
super.viewDidLoad()
// NSUserDefaults().removeObjectForKey("endTime")
// loads endTime if it exists otherwise assign 0 value
endTime = NSUserDefaults().valueForKey("endTime") as? NSTimeInterval ?? 0
// restart timer if endTime exists
if endTime > 0 {
tasksManager = NSTimer.scheduledTimerWithTimeInterval(1/15, target: self, selector: "updateTime", userInfo: nil, repeats:true)
} else {
strTimer.text = "0:01:00.00"
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
#IBAction func startTimer (sender: AnyObject) {
// sets endTime new timeinterval to a future point in time
// so we need to add n seconds from now
endTime = now + 60.0 // now + n seconds
// saves it using NSUserDefaults
NSUserDefaults().setValue(endTime, forKey: "endTime")
// if the timer doest exists we create one
if !tasksManager.valid {
tasksManager = NSTimer.scheduledTimerWithTimeInterval(1/30, target: self, selector: "updateTime", userInfo: nil, repeats:true)
// if the timer exists we invalidate it
} else {
tasksManager.invalidate()
endTime = 0
strTimer.text = "0:01:00.00"
NSUserDefaults().removeObjectForKey("endTime")
}
}
}
extension NSTimeInterval {
var time: String {
return String(format: "%d:%02d:%02d.%02d", Int(self/3600), Int(self/60%60), Int(self%60), Int(self*100%100))
}
}

Answer 2

You can save the current date and time in NSUserDefaults like this.
NSUserDefaults.standardUserDefaults().setObject(NSDate(), forKey: "dateKey")
You can calculate the number of minutes elapsed between saved time and current time in this way.
if let savedDate = NSUserDefaults.standardUserDefaults().objectForKey("dateKey") as? NSDate
{
let currentDate = NSDate()
let distanceBetweenDates = currentDate.timeIntervalSinceDate(savedDate)
let secondsInAnMinute = 60.0;
let minutesElapsed = distanceBetweenDates / secondsInAnMinute;
println(minutesElapsed)
println(distanceBetweenDates)
}