something.swift

    func textFieldDidBeginEditing(textField: UITextField) {
        print(textField.tag)
        switch textField.tag {
        case 0:
            if textField.text == "First name" { textField.text = nil }
        case 1:
            if textField.text == "Last name" { textField.text = nil }
        default:
            textField.text = nil
        }
    }
    
    func textFieldDidEndEditing(textField: UITextField) {
        switch textField.tag {
        case 0:
            if textField.text == "" {
                textField.text = "First name"
            }
        case 1:
            if textField.text == "" {
                textField.text = "Last name"
            }
        default:
            return
        }
    }
    
    func textFieldShouldReturn(textField: UITextField) -> Bool {
        switch textField {
        case firstNameField:
            return lastNameField.becomeFirstResponder()
        case lastNameField:
            return lastNameField.resignFirstResponder()
        default:
            return false
        }
    }