Запуск цикла сообщений в потоке

Я бы предложил запустить класс из SRC:

import Foundation
import UIKit

// Don't forget the delegate!
class ViewController: UIViewController, UITextFieldDelegate {

required init(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

@IBOutlet var myTextField : UITextField?

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    self.myTextField.delegate = self;
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func textFieldShouldReturn(textField: UITextField!) -> Bool {
    self.view.endEditing(true);
    return false;
}

}