Invalid selector error on setting delegate: Xcode 10 swift 4

Question

The app crashes on the line where I set the TextField delegate:

listNameTextField = self

in the viewDidLoad method

Gives error

'NSInvalidArgumentException', reason: '-[UIView setDelegate:]: unrecognized selector sent to instance

I have already tried to make the listNameTextField variable strong over weak reference but it does not change the problem

import UIKit

class CreateListViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var listNameTextField: UITextField!
    var listNameString: String = ""

    override func viewDidLoad() {
        super.viewDidLoad()
        self.title = "Create List"
        listNameTextField.delegate = self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    @IBAction func submitListName(_ sender: UIButton) {
        if listNameString != "" {
            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            let controller = storyboard.instantiateViewController(withIdentifier: "ListView")
            self.present(controller, animated: true, completion: nil)
        }
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {

        textField.resignFirstResponder()
        return true
    }

    func textFieldDidEndEditing(_ textField: UITextField) {

        if let text = listNameTextField.text {
            listNameString = text
        }
    }
}

Answer 1

According to your error, your listNameTextField is just UIView.
Check connections in your xib/storyboard.

You can't change type of UIView in storyboard to UITextField, since storyboard generate additional properties in xml for UITextField.

Instead you need to delete your original UIView from storyboard and add new UITextField and make new connection.