At the very bottom is my code where MainController initiates a subview called setController. The new subview is created when I click the button
However, within setController's code I get back a nil when I try to the superview:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
print("\(self.view.superview)" ?? "count->no parent")
}
I am assigning the second view as a subview, but obviously I am missing something. Have I misunderstood how UIView hierarchy works?
class MainController: UIViewController {
private lazy var setController = SetController()
var invButton : MyButton!
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .black
invButton = makeButton(vControl: self, btype: ButtType.inv, action: #selector(self.buttonAction(sender:)))
invButton.frame.origin.x = self.view.frame.width * 0.1
invButton.frame.origin.y = self.view.frame.height * 0.1
invButton.setTitle("Settings", for: .normal)
}
override var prefersStatusBarHidden: Bool {
return false
}
@objc func buttonAction(sender: UIButton!) {
guard let theButton = sender as? MyButton else { return}
UIView.transition(with: self.view, duration: 0.5, options: .transitionCurlDown, animations: { [self] in
self.addChild(setController)
self.view.addSubview(setController.view)
setController.didMove(toParent: self)
}, completion: nil)
}
}
See the Apple document excerpt below. If calling animation didMove(toParent:) is called after the transition not inside of the animation block, no animation the immediately after the addChild.
With animation
@objc func buttonAction(sender: UIButton!) {
guard let theButton = sender as? MyButton else { return}
UIView.transition(with: self.view, duration: 0.5, options: .transitionCurlDown, animations: { [self] in
self.addChild(setController)
self.view.addSubview(setController.view)
}, completion: {
setController.didMove(toParent: self)
})
}
No animation
@objc func buttonAction(sender: UIButton!) {
guard let theButton = sender as? MyButton else { return}
self.view.addSubview(setController.view)
self.addChild(setController)
setController.didMove(toParent: self)
}
Discussion Your view controller can override this method when it wants to react to being added to a container. If you are implementing your own container view controller, it must call the didMove(toParent:) method of the child view controller after the transition to the new controller is complete or, if there is no transition, immediately after calling the addChild(_:) method. The removeFromParent() method automatically calls the didMove(toParent:) method of the child view controller after it removes the child.
Sundel: https://www.swiftbysundell.com/basics/child-view-controllers/
