问如果条件为True，则在执行分段之前

EN

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "showVCA" {
        if let vc_A = segue.destination as? ViewControllerA {
            vc_A.validPincode = validPincode
            vc_A.participants = participants
            vc_A.event = event
        }
    }
}



@IBAction func backbutton(_ sender: UIButton) {
    let alert = SCLAlertView(appearance: confirmationAppearance)
    _ = alert.addButton("Leave", action: {
        self.dismiss(animated: true, completion: nil)
        if validation() {
            self.performSegue(withIdentifier: "showVCA", sender: sender)
        }

    })
    _ = alert.addButton("Stay", action: { })
    _ = alert.showError("Confirmation", subTitle: "Are you sure you want to leave this page?")

}

func validation() -> Bool {
     // add validation logic here
     return false
}