Prepare for Segue function not passing data correctly - ios

Question

My prepareForSegue method isn't passing data to the destination view controller.
var buttonsDictionary = [Int: UIButton]()
func createButtonArray() {
for item in statTitles {
let statisticButton = StatButton()
statisticButton.layer.cornerRadius = 10
statisticButton.backgroundColor = UIColor.darkGray
statisticButton.setTitle(String(item.value), for: UIControlState.normal)
statisticButton.setTitleColor(UIColor.white, for: UIControlState.normal)
statisticButton.titleLabel?.font = UIFont.systemFont(ofSize: 43)
statisticButton.titleEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 0)
statisticButton.contentHorizontalAlignment = .left
statisticButton.addTarget(self, action: #selector(displayStatDetail), for: .touchUpInside)
statisticButton.buttonIndex = item.key
buttonsDictionary[item.key] = (statisticButton) // Assign value at item.key
print(statisticButton.buttonIndex)
}
}
func viewSavedStatistics() {
for button in buttonsDictionary {
statisticsView.addArrangedSubview(button.value)
}
}
#objc func displayStatDetail() {
self.performSegue(withIdentifier: "StatDetailSegue", sender: UIButton())
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "StatDetailSegue" {
if let destinationVC = segue.destination as? StatDetailViewController,
let index = (sender as? StatButton)?.buttonIndex {
destinationVC.statID = index
print("Destination STATID: \(destinationVC.statID)")
}
}
}
All of the above code is written in the ViewController class.
StatButton is a custom UIButton class.
The prepare is meant pass on the buttonIndex of the tapped button, but only passes on 0 and doesn't print so I don't think it's being called.

Answer 1

You sender is a new instance of UIButton which doesn't have any of the information you need. Instead pass the button calling the selector.
#objc func displayStatDetail(_ sender: StatisticButton) {
self.performSegue(withIdentifier: "StatDetailSegue", sender: sender)
}
You would need to change the target selector like this in the loop.
statisticButton.addTarget(self, action: #selector(displayStatDetail(_:)), for: .touchUpInside)

Answer 2

You’re passing a new instance of UIButton as sender here:
self.performSegue(withIdentifier: "StatDetailSegue", sender: UIButton())
Instead you should probably have your statisticButton there. Your button target selector method can have a parameter - the button instance the user clicked on. Use it as sender.

Answer 3

You had a mistake in performSeguefunction you've send always a new object of UIButton, not the one you've clicked on. Here is what you should do.
statisticButton.addTarget(self, action: #selector(displayStatDetail(_ :)), for: .touchUpInside)
#objc func displayStatDetail(_ sender: UIButton) {
self.performSegue(withIdentifier: "StatDetailSegue", sender: sender)
}