How to rewrite this encoding for a UISwitch and also how to decode it?

I'm trying to save the state of some switches and restore it when the app launches again but when I wrote this :

override func encodeRestorableState(with coder: NSCoder) {
    super.encodeRestorableState(with: coder)
    coder.encode(Int32(self.runSwitch1.state.rawValue), forKey: CodingKey.Protocol)
}

I got this error :

Cannot convert value of type 'CodingKey.Protocol.Type' to expected argument type 'String'

What should I do ?

If you mean't was restoring state between app switches provide a unique key against the type to be encoded

override func encodeRestorableStateWithCoder(coder: NSCoder) {
    coder.encode(self.runSwitch1.isOn, forKey: "switchState")    
  super.encodeRestorableStateWithCoder(coder)
}

//Decode later when state restore

override func decodeRestorableStateWithCoder(coder: NSCoder) {          
  super.decodeRestorableStateWithCoder(coder)
}

And restore switch state by

override func applicationFinishedRestoringState() {
   let restoredState =coder.decodeBool(forKey: "switchState") 
   self.switch.setOn(restoredState, animated: false)
}

Use CoreData or other db based framework to sustain states even after app is closed. Or you can do it using userdefaults

class MySavedSwitchStates:NSObject {
    var userDefault = UserDefaults.standard
    private override init() {
    }
    static let shared = MySavedSwitchStates()

    //This saves state to preferences
    func setSwitchState(_ state:Bool) {
        userDefault.set(state, forKey: "SOME_SWITCH_STATE")
    }

    //This retrieve the current state of switch
    func retrieveSwitchState() -> Bool {    
        return userDefault.bool(forKey: "SOME_SWITCH_STATE")
    }
}

and in your controller

//In your controller viewdidLoad
let restoredState = MySavedSwitchStates.shared.retrieveSwitchState()
self.switch.setOn(restoredState, animated: false)