How do i keep UISwitch state when changing ViewControllers? - ios

Question

When I move from one view controller to another, the switch on the first controller resets itself and does not retain its state.
How can I make it save its state when come back to it after viewing other controllers? And how do I make it save its state after closing the app. I have looked at the various stackOverflow questions and responses and the apple documentation, but nothing seems to work.
Here is my class for the View Controller that has the switch.
class Days: UIViewController {
#IBOutlet weak var switchButton: UISwitch!
var switchState = true
let switchKey = "switchState"
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
#IBAction func saveSwitchPressed(sender:AnyObject) {
if self.switchButton.on {
self.switchState = true
NSUserDefaults.standardUserDefaults().setBool(self.switchState, forKey: switchKey)
NSUserDefaults.standardUserDefaults().synchronize()
println(NSUserDefaults.standardUserDefaults().boolForKey(switchKey))
} else {
self.switchState = false
NSUserDefaults.standardUserDefaults().setBool(self.switchState, forKey: switchKey)
NSUserDefaults.standardUserDefaults().synchronize()
println(NSUserDefaults.standardUserDefaults().boolForKey(switchKey))
}
}
}
I'm a beginner to Swift and generally Xcode. Thank you in advance for your time and help :)

Answer 1

Xcode 8.3 • Swift 3.1
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var switchButton: UISwitch!
override func viewDidLoad() {
super.viewDidLoad()
switchButton.isOn = UserDefaults.standard.bool(forKey: "switchState")
}
#IBAction func saveSwitchPressed(_ sender: UISwitch) {
UserDefaults.standard.set(sender.isOn, forKey: "switchState")
}
}

Answer 2

Since you're syncing the on/off state of the switch you could on viewWillAppear: or viewDidAppear: set the state of the switch to the value stored in NSUserDefaults
Something along the lines of
override func viewWillAppear(animated: Bool) {
self.switchButton.on = NSUserDefaults.standardUserDefaults().boolForKey(switchKey)
}

Answer 3

just after code connect UISwitch to IBoutlet.
class ViewController: UIViewController {
#IBOutlet weak var switchButton: UISwitch!
#objc func switchStateDidChange(_ sender:UISwitch!)
{
if (sender?.isOn == true){
print("on")
}
else {
print("off")
}
UserDefaults.standard.set(sender.isOn, forKey: "switchState")
UserDefaults.standard.synchronize()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(false)
switchButton?.isOn = UserDefaults.standard.bool(forKey: "switchState")
switchButton?.addTarget(self, action: #selector(switchStateDidChange(_:)), for: .touchUpInside)
}
}