How to hide the keyboard using ‘done’ button Swift 4

use below code

class ViewController: UIViewController,UITextFieldDelegate

  // set delegate in didLoad
     override func viewDidLoad() {
       super.viewDidLoad()
       textField.delegate = self
     }


   // MARK: - Search Method
    func textFieldShouldReturn(_ textField: UITextField) -> Bool
    {

        textField.resignFirstResponder()
        return true
    }

Set the delegate on the text field and implement this method. Should do the trick.

func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    textField.resignFirstResponder()
    return true
}