Swift: Calling the same method from two different buttons - swift

Question

When I tap the orangeButtonOne in the left corner of the screen, my collectionView appears, and when I tap the orangeButtonOne again the collectionView disappears. This works fine but now... the collectionView as you can see also holds a lot of buttons and when I press one of them it calls the exact same method as orangeButtonOne that is closeDropDownView. However, when I tap a button in the collectionView the app crashes on line 99.. and I get the following error:
class TestViewController: UIViewController {
#IBOutlet weak var dropDownView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
dropDownView.isHidden = true
func closeDropDownView() {
UIView.animate(withDuration: 0.3, delay: 0, options: .curveLinear, animations: {
99 var dropTopFrame = self.dropDownView.frame <THREAD1: FATAL ERROR: UNEXPECTEDLY FOUND NIL WHILE IMPLICITLY UNWRAPPING AN OPTIONAL VALUE
var dropBottomFrame = self.dropDownView.frame
dropTopFrame.origin.y += dropBottomFrame.size.height
dropBottomFrame.origin.y -= dropTopFrame.size.height
self.dropDownView.frame = dropTopFrame
self.dropDownView.frame = dropBottomFrame
UIView.animate(withDuration: 0.5) {
self.dimView.alpha = 0
}
}, completion: { finished in
self.dropDownView.isHidden = true
print("dropView closed!")
})
}
}
I don't understand how this method works fine when the orangeButtonOne calls it but then when a collectionView button calls this method the frame value is suddenly nil?
Here is how each button calls the closeDropDownView method:
class TestViewController: UIViewController {
//viewDidLoad etc
#IBAction func orangeButtonOneTapped(_ sender: Any) {
if (dropDownView.isHidden == true ) {
openDropDownView()
}
else { closeDropDownView() }
}
extension DropDownViewController: UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
let testVC = TestViewController()
#objc func CVButtonTapped(sender: UIButton!) {
print("button tapped")
testVC.closeDropDownView()
}
}

Answer 1

You're getting a crash because you are creating a new instance of TestViewController in DropDownViewController and calling closeDropDownView method on that particular instance(testVC). In a new instance of TestViewController the #IBOutlet var dropDownView is empty when you just initialize it and hence you get a crash. To avoid the crash you need to pass the same instance of TestViewController to DropDownViewController to call the exact same instance of closeDropDownView to get the same functionality instead of a crash.