[iOS]フォーカスが外れたタイミングでキーボードを隠す ref: http://qiita.com/katzhide/items/8bab35e027fca49654c8

hideKeyboard.swift

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {
    @IBOutlet weak var textField: UITextField!

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        view.endEditing(true)
    }
}