Am having trouble moving code into a separate function - swift

Question

From within my GameViewController's viewDidLoad() function I do two things:
1- I create a sub UIVIew, myView, which is added to the main view,
2- I call my function, addConstraints, which is in the GameViewController's code.
When I create GameScene, self.myView.frame.width & self.myView.frame.height contain the correct values, and abide by the safeAreaLayout guides.
I want to make my code clearer, so I've moved the addConstraints function to a separate file. But when I run my app that way self.myView.frame.width & self.myView.frame.height are zero.
So am curious if I am somehow translating the function incorrectly, or maybe this is something I can't move outside of the main code?
The first block is the original code, the 2nd is the function
//located with GameViewControl
private func addConstraints(){
var constraints = [NSLayoutConstraint]()
constraints.append(myView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
constraints.append(myView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
constraints.append(myView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
constraints.append(myView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
NSLayoutConstraint.activate(constraints)
}
translated into a function
//called from GameViewControl
createConstraints(view: myView)
....
//located outside of GameViewControl
func createConstraints(view: UIView) {
var constraints = [NSLayoutConstraint]()
constraints.append(view.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
constraints.append(view.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
constraints.append(view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
constraints.append(view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
NSLayoutConstraint.activate(constraints)
}
And here is the full file of GameViewControl
import UIKit
import SpriteKit
class GameViewController: UIViewController {
private let myView : UIView = {
let myView = UIView()
setViewAttributes(view: myView)
return myView
}()
private func addConstraints(){
var constraints = [NSLayoutConstraint]()
//add
constraints.append(myView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
constraints.append(myView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
constraints.append(myView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
constraints.append(myView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
//activate
NSLayoutConstraint.activate(constraints)
}
override func viewDidLoad() {
super.viewDidLoad()
#if DEBUG
print ("viewDidLoad")
#endif
if let view = self.view as! SKView? {
getScreenDimensions (screen: &screenDims)
view.addSubview(myView)
addConstraints()
var scene : GameScene!
DispatchQueue.main.async { scene = GameScene(size: CGSize(width: self.myView.frame.width, height: self.myView.frame.width))
scene.anchorPoint = CGPoint(x: 0.0, y: 0.0)
scene.backgroundColor = .clear
scene.scaleMode = .aspectFit
view.isHidden = false
view.presentScene(scene)
}
view.ignoresSiblingOrder = true
view.showsFPS = true
view.showsNodeCount = true
view.showsPhysics = true
}
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
#if DEBUG
print ("GVC viewDidLayoutSubviews")
#endif
myGlobalVars.sceneRect = view.frame
if #available(iOS 11.0, *) {
myGlobalVars.topSafeArea = view.safeAreaInsets.top
myGlobalVars.bottomSafeArea = view.safeAreaInsets.bottom
} else {
myGlobalVars.topSafeArea = topLayoutGuide.length
myGlobalVars.bottomSafeArea = bottomLayoutGuide.length
}
}
override var shouldAutorotate: Bool {
#if DEBUG
print ("shouldAutorotate")
#endif
return false
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
#if DEBUG
print ("supportedInterfaceOrientations")
#endif
if UIDevice.current.userInterfaceIdiom == .phone {
return .allButUpsideDown
} else {
return .all
}
}
override var prefersStatusBarHidden: Bool {
#if DEBUG
print ("prefersStatusBarHidden")
#endif
return false
}
}
The call to function setViewAttributes does pass the view to a function, and I have verified that that function is working.
func setViewAttributes(view: UIView)
{
view.alpha = 0.0
view.frame.size.height = UIScreen.main.nativeBounds.height
view.frame.size.width = UIScreen.main.nativeBounds.width
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = .clear
}

Answer 1

You can't just move this kind of function because the view variable inside it refers to GameViewController.view.
If you want to do a refactor like this you can move this method to an extension and call it inside your GameViewController.
public extension UIView {
func createConstraints() {
guard let superview = superview else { return }
view.translatesAutoresizingMaskIntoConstraints = false
var constraints = [NSLayoutConstraint]()
constraints.append(leadingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.leadingAnchor))
constraints.append(trailingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.trailingAnchor))
constraints.append(bottomAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.bottomAnchor))
constraints.append(topAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.topAnchor))
NSLayoutConstraint.activate(constraints)
}
}
And then instead of calling addConstraints() in viewDidLoad() you should call myView.createConstraints(). It should work the same as before.
You can read more about extension from Extensions — The Swift
Programming Language.
And also you should read this too Programmatically Creating
Constraints

Answer 2

After going through the code, over and over I realized I was calling the safeAreaLayout routine before viewDidLayoutSubviews. Now I can move my call to a function and it works. Now I'd love to know why it was working before, when I was calling it prematurely. But maybe I should be grateful that I found a substantial error.
So now my code looks the same as the code in the OP, except every call regarding screen dimensions, and safeAreaLayout, are done in the viewDidLayoutSubviews function.
And addConstraints is now an external function
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
getScreenDimensions (screen: &screenDims)
view.addSubview(myView)
addConstraints()
myGlobalVars.sceneRect = view.frame
createConstraints(view: myView)
if #available(iOS 11.0, *) {
myGlobalVars.topSafeArea = view.safeAreaInsets.top
myGlobalVars.bottomSafeArea = view.safeAreaInsets.bottom
} else {
myGlobalVars.topSafeArea = topLayoutGuide.length
myGlobalVars.bottomSafeArea = bottomLayoutGuide.length
}
}