ViewController.swift

import UIKit

extension UIView {
    
    func traverseResponderChainForUIViewController() -> UIViewController? {
        
        guard let nextResponder = self.next else {
            return nil
        }
        
        if nextResponder is UIViewController {
            return nextResponder as? UIViewController
        }
        else if nextResponder is UIView {
            return (nextResponder as? UIView)?.traverseResponderChainForUIViewController()
        }
        else {
            return nil
        }
    }
    
    func viewController() -> UIViewController? {
        return self.traverseResponderChainForUIViewController()
    }
    
    var key: String {
        
        guard let vc = self.viewController() else {
            return ""
        }
        
        var numIvars: UInt32 = 0
        guard let ivars = class_copyIvarList(type(of: vc), &numIvars) else {
            return ""
        }
        
        var k = ""
        
        for i in 0..<numIvars {
            
            let index = Int(i)
            
            let ivar = ivars[index]
            
            if self == object_getIvar(vc, ivar) as? UIView, let ivarName = String.init(utf8String: ivar_getName(ivar)!) {
                k = ivarName
                break
            }
        }
        
        free(ivars)
        
        return k
    }
}

class ViewController: UIViewController {
    
    let testView = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        self.view.addSubview(testView)
        
        DispatchQueue.main.async {
            print("key: \(self.testView.key)")
        }
    }


}