A UIView helper extension that finds the 'key' view in the controller's hierarchy. Useful for finding a UITableView/UICollectionView or any other view that's NOT the controller's root view.

UIView+KeyView..swift

import UIKit

internal extension UIViewController {

    /// Returns the 'key' view for this controller. I.e. the top-most visible view that covers the view's entire bounds.
    /// This is generally the controller's root view, but it could also be a nested table/collection view, etc...
    @objc var _keyView: UIView {
        return view._keyViews(in: self).last ?? view
    }

}

internal extension UIView {

    /// Returns all potentional 'key' views in this controller
    /// - Parameter controller: The controller to search
    @objc func _keyViews(in controller: UIViewController) -> [UIView] {
        let views = subviews.filter { $0._isKeyView(in: controller) }
        return views + views.flatMap { $0._keyViews(in: controller) }
    }

    /// Returns true if this view is a 'key' in the specified controller
    /// - Parameter controller: The controller to search
    @objc func _isKeyView(in controller: UIViewController) -> Bool {
        return alpha > 0
            && !isHidden
            && isUserInteractionEnabled
            && (frame.size == controller.view.safeAreaLayoutGuide.layoutFrame.size
                || frame.size == controller.view.bounds.size)
    }

}