UIViewController Subclass does not recognize UITapGesture - ios

Question

With the intention to slim down my viewcontroller a little bit, i want to move the ui elements and corresponding functions into a subclass. but then my gestures don't work. how can i solve this?
MyViewController.swift
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
SubclassMyViewController().setupUserInterface(view: view)
}
#objc func doSomething() {
log.info("logo was tapped")
}
}
SubclassMyViewController.swift
class SubclassMyViewController: MyViewController {
func setupUserInterface(view: UIView) {
// ...
view.addSubview(logoImage)
logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
logoImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
logoImage.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
}
lazy var logoImage: UIImageView = {
let imageView = UIImageView()
imageView.image = UIImage(named: "logo")
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFit
// ADD GESTURE
let tap = UITapGestureRecognizer(target: self, action: #selector(doSomething))
imageView.isUserInteractionEnabled = true
imageView.addGestureRecognizer(tap)
return imageView
}()
}
Putting everything into the Viewcontroller does work. if I split it in two classes, the gesture won't be recognized.. Thanks!

Answer 1

I think you're confusing some things here.
SubclassMyViewController().setupUserInterface(view: view) this line creates an instance of SubclassMyViewController, which in your code sample owns the image view. Because you don't have any references to the created subclass however, it will die as soon as this line is done executing.
You could accomplish your goal by creating a static helper class instead. Here's how that would look.
class MyViewController: UIViewController {
var imageView: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
MyViewControllerSetupHelper.setupUserInterface(viewController: self)
}
#objc func doSomething() {
log.info("logo was tapped")
}
}
class MyViewControllerSetupHelper {
static func setupUserInterface(viewController: MyViewController) {
let view = viewController.view!
let imageView = getLogoImageView()
viewController.imageView = imageView
let tapGesture = UITapGestureRecognizer(target: viewController, action: #selector(MyViewController.doSomething))
imageView.addGestureRecognizer(tapGesture)
view.addSubview(imageView)
NSLayoutConstraint.activate([
imageView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
imageView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
imageView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5)
])
}
static func getLogoImageView() -> UIImageView {
let imageView = UIImageView()
imageView.image = UIImage(named: "logo")
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFit
imageView.isUserInteractionEnabled = true
return imageView
}
}

Answer 2

SubclassMyViewController().setupUserInterface(view: view) is creating a new instance of subclass, but the reference of the instance is not stored.
Swift will deallocate the class if there is no reference (refer to ARC).
The lazy var logoImage is adding a GestureRecognizer which points to the doSomething() of the SubclassMyViewController-instance, which is deallocated immediately.
It would work if you do this (THIS IS NOT GOOD):
class ViewController: UIViewController {
var x: SubclassMyViewController!
override func viewDidLoad() {
super.viewDidLoad()
x = SubclassMyViewController()
x.setupUserInterface(view: view)
}
#objc func doSomething() {
log.info("logo was tapped")
}
}
You should fix your design, because:
ViewController is accessing SubclassMyViewController, which is, however, a subclass of ViewController

Answer 3

You doing really strange things. Gesture recognizer added to SubclassMyViewController instance. Which seams removed after creation.
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
SubclassMyViewController().setupUserInterface(view: view, vc: self)
}
#objc func doSomething() {
log.info("logo was tapped")
}
}
class SubclassMyViewController: MyViewController {
func setupUserInterface(view: UIView, vc: UIViewController) {
// ...
view.addSubview(logoImage)
logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
logoImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
logoImage.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
let tap = UITapGestureRecognizer(target: vc, action: #selector(doSomething))
logoImage.isUserInteractionEnabled = true
logoImage.addGestureRecognizer(tap)
}
lazy var logoImage: UIImageView = {
let imageView = UIImageView()
imageView.image = UIImage(named: "logo")
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFit
return imageView
}()
}
P.S. code is really dirty.. don't do like this
Edit
Probably this is what you wanna do:
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
SubclassMyViewController().setupUserInterface(view: view, vc: self)
}
#objc func doSomething() {
log.info("logo was tapped")
}
func setupUserInterface(view: UIView) {
// ...
view.addSubview(logoImage)
logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
logoImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
logoImage.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
let tap = UITapGestureRecognizer(target: self, action: #selector(doSomething))
logoImage.isUserInteractionEnabled = true
logoImage.addGestureRecognizer(tap)
}
lazy var logoImage: UIImageView = {
let imageView = UIImageView()
imageView.image = UIImage(named: "logo")
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFit
return imageView
}()
}