Swift 3 - If else statement based on button state - ios

Question

I am really new to Swift and working on my first project (I have a bit of experience with Javascript and web development). I have run into trouble (going on 4 hours of trying different solutions).
I have an app where when a UIButton is pushed it logs a value to FireBase (ON). When it is pushed a second time it logs (OFF) to the database.
When I make the button change the view.backgroundColor and put if else tied to the colour it works.
But I can't for the life of me figure out how to build my if else based on the state of the button. I have now ended up trying to change the colour of the button itself and tie the if else to that. Which I know is a really messy improper way to go about it.
import UIKit
import Firebase
import FirebaseDatabase
class ViewController: UIViewController {
#IBAction func OnOffButton(_ sender: UITapGestureRecognizer){
if button.backgroundColor == UIColor.white {
OnOff(state:"ON")
OnOffButton.backgroundColor = UIColor.blue
} else{
OnOff(state:"OFF")
OnOffButton.backgroundColor = UIColor.white
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
OnOff(state: "Off")
OnOffButton.backgroundColor = UIColor.white
}

Answer 1

UIButton inherits from UIControl which has an isSelected property. Use this to track state. Typically you'll use button.isSelected == true to correspond to your on state, and false is your off state.
To toggle state you can use button.isSelected = !button.isSelected.
For your specific example:
// User pressed the button, so toggle the state:
button.isSelected = !button.isSelected
// Now do something with the new state
if button.isSelected {
// button is on, so ...
} else {
// button is off, so...
}

Answer 2

Here’s a quick and dirty implementation of Duncan C’s suggestion to use a buttonIsSelected variable to store the button state:
import UIKit
class ViewController: UIViewController {
var buttonIsSelected = false
#IBOutlet weak var onOffButton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
updateOnOffButton()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func onOffButtonTapped(_ sender: Any) {
buttonIsSelected = !buttonIsSelected
updateOnOffButton()
}
func updateOnOffButton() {
if buttonIsSelected {
onOffButton.backgroundColor = UIColor.blue
}
else {
onOffButton.backgroundColor = UIColor.white
}
}
}

Answer 3

Par's solution should work. However, I would suggest a different approach.
In general it's not good design to store state in a view object. It's fragile, and doesn't follow the MVC design pattern, where view objects display and collect state information, not store it.
Instead I would create an instance variable in your view controller, buttonIsSelected. Toggle that when the button is tapped, and have it change the state of the button's selected property, the button's color, AND log the new state to FireBase.
If you store more complex state in your view controller it would be worth separating that out into a model object. It can be as simple as a struct that holds the different state values. That way you have a clear separation between your controller (view controller) and model.