Add image to TextField on left side - Swift 3

// Vladimir Zhelnov - neatek.pw - Web/iOS dev
class ViewController: UIViewController {
    @IBOutlet weak var textfield: UITextField!

    override func viewDidLoad() {
        textfield.leftViewMode = UITextFieldViewMode.always
        let imageView = UIImageView(frame: CGRect(x: 40, y: 0, width: 40, height: 15)) // here size of Image, width = 40 is spacing from left side
        imageView.image = UIImage(named: "HERE_IS_NAME_OF_FILE")
        imageView.contentMode = UIViewContentMode.scaleAspectFit
    }
}