How to dismiss keyboard when touching anywhere outside UITextField (in swift)?

Try this, it's tested and working:

For Swift 3.0 / 4.0

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

For Older Swift

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

swift 3

override func viewDidLoad() {
    super.viewDidLoad()
    self.view.addGestureRecognizer(UITapGestureRecognizer(target: self.view, action: #selector(UIView.endEditing(_:))))
}

In this case, there is UITapGesture as one of the choices. I tried to create sample code just in case. Like this,

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var scrollView: UIScrollView!

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

        let tapGesture = UITapGestureRecognizer(target: self, action: "tap:")
        view.addGestureRecognizer(tapGesture)
    }

    func tap(gesture: UITapGestureRecognizer) {
        textField.resignFirstResponder()
    }
}

Edited for Swift 4

Edit: Added @objc. While this isn't the best option for performance, one instance of it here shouldn't cause too many problems until there is a better solution.

Edited to fix when needing to interact with items behind GestureRecognizer.

Edit: Thanks @Rao for pointing this out. Added tap.cancelsTouchesInView = false.

This should help you with having multiple UITextView or UITextField

Create an extension of the view controller. This has worked much smoother for me and with less hassle than trying to use .resignFirstResponder()

extension UIViewController
{
    func setupToHideKeyboardOnTapOnView()
    {
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(
            target: self,
            action: #selector(UIViewController.dismissKeyboard))

        tap.cancelsTouchesInView = false
        view.addGestureRecognizer(tap)
    }

    @objc func dismissKeyboard()
    {
        view.endEditing(true)
    }
}

Call self.setupToHideKeyboardOnTapOnView() in the viewDidLoad