Swift 3 & 4 Dismiss Keyboard

In viewDidLoad:

//Dissmiss Keyboard
let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.dismissKeyboard))
view.addGestureRecognizer(tap)

Function:

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