“unrecognized selector sent to instance” when keyboard appears

Question

When I click a text field into my app screen and the keyboard is showing up xcode debugger shows this error:

[mainViewController keyboardWasShown]: unrecognized selector sent to instance 0x5867ac0

In the viewDidLoad method of the mainViewController I'm calling the registerForKeyboardNotifications method like that:

[self registerForKeyboardNotifications];

Here's its implementation (in mainViewController.m):

- (void)registerForKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWasShown:) name:UIKeyboardDidShowNotification object:nil];
   [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillBeHidden:) name:UIKeyboardWillHideNotification object:nil];
}

// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{

}

// Called when the UIKeyboardWillHideNotification is sent
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{

}

Any idea what could be wrong?

Answer 1

Make sure the notification selector has the colon at the end; this is important, keyboardWasShown and keyboardWasShown: are different selectors.