Prepare for Segue function not passing data correctly

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)