executing a customizable function after an animation - swift

Question

I'm trying to execute a function after an animation. This will need to be a different function each time so I introduced an argument as a CGFunction. What's weird though is that when I'm running this code I actually get "yes" printed to console which means that it's working fine. But the program crashes a few seconds later, and what's even weirder is that "view running" actually never gets printed to console. If anybody could take a look and let me know what's causing this problem I'd really appreciate it. Thanks.
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
addWelcomeLabel()
print("view running")
}
func addWelcomeLabel() {
let welcomeLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 500, height: 100))
welcomeLabel.alpha = 0.0
welcomeLabel.center = CGPoint(x: self.view.center.x, y: self.view.center.y)
welcomeLabel.text = "Welcome"
welcomeLabel.textAlignment = .center
welcomeLabel.font = UIFont.boldSystemFont(ofSize: 50)
welcomeLabel.textColor = UIColor(displayP3Red: 160/255, green: 160/255, blue: 160/255, alpha: 160/255)
view.addSubview(welcomeLabel)
fadeViewInThenOut(view: welcomeLabel, delay: 5, afterCompletion: hello() as! CGFunction)
}
func fadeViewInThenOut(view: UILabel, delay: TimeInterval, afterCompletion: CGFunction) {
let animationDuration = 1.00
let action = afterCompletion
UIView.animate(
withDuration: animationDuration,
delay: 1,
animations: { () -> Void in view.alpha = 1}) { (Bool) -> Void in
UIView.animate(
withDuration: animationDuration,
delay: delay,
animations: { () -> Void in view.alpha = 0},
completion: { finished in action //insert here what i want it to do after
})
}
}
func hello(){
print("yes")
}
}

Answer 1

override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
addWelcomeLabel()
}
func addWelcomeLabel() {
let welcomeLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 500, height: 100))
welcomeLabel.alpha = 0.0
welcomeLabel.center = CGPoint(x: self.view.center.x, y: self.view.center.y)
welcomeLabel.text = "Welcome"
welcomeLabel.textAlignment = .center
welcomeLabel.font = UIFont.boldSystemFont(ofSize: 50)
welcomeLabel.textColor = UIColor(displayP3Red: 160/255, green: 160/255, blue: 160/255, alpha: 160/255)
view.addSubview(welcomeLabel)
fadeViewInThenOut(view: welcomeLabel, delay: 5, afterCompletion: hello())
}
func fadeViewInThenOut(view: UILabel, delay: TimeInterval, afterCompletion: (())) {
let animationDuration = 1.00
let action = afterCompletion
UIView.animate(
withDuration: animationDuration,
delay: 1,
animations: { () -> Void in view.alpha = 1}) { (Bool) -> Void in
UIView.animate(
withDuration: animationDuration,
delay: delay,
animations: { () -> Void in view.alpha = 0},
completion: { finished in action //insert here what i want it to do after
print("action")
})
}
}
func hello(){
print("yes")
}
}