Note: set Attributes inspector property of UITextField

Clear Button -> Appears while editing

so it will display 'X' button while editing in textfield.

// Objective-C

-(BOOL)textFieldShouldClear:(UITextField *)textField
{
    textField.text = @"";
    [textField resignFirstResponder];
    return NO;
}

// Swift

func textFieldShouldClear(textField: UITextField) -> Bool {
    textField.text = ""
    textField.resignFirstResponder()
    return false
}