show alert with textfield swift

//1. Create the alert controller.
let alert = UIAlertController(title: "Some Title", message: "Enter a text", preferredStyle: .alert)

//2. Add the text field. You can configure it however you need.
alert.addTextField { (textField) in
    textField.text = "Some default text"
}

// 3. Grab the value from the text field, and print it when the user clicks OK.
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak alert] (_) in
    let textField = alert.textFields![0] // Force unwrapping because we know it exists.
    print("Text field: \(textField.text)")
}))

// 4. Present the alert.
self.present(alert, animated: true, completion: nil)