Question

Most likely a dumb question, but what’s the difference between:

UIBarButtonItem *anotherButton = [[UIBarButtonItem alloc] initWithTitle:@"Join" style:UIBarButtonItemStylePlain
                                target:self action:@selector(pressJoinButton)];

and

UIBarButtonItem *anotherButton = [[UIBarButtonItem alloc] initWithTitle:@"Join" style:UIBarButtonItemStylePlain
                                target:self action:@selector(pressJoinButton:)];

Notice how one is pressJoinButton, and the other is pressJoinButton:

Answer 1

The colon is used to add arguments to the method you are calling, so if pressJoinButton had zero arguments, it would be:

pressJoinButton

If it had one argument, it would be:

pressJoinButton:

if it had 2 arguments, it would be:

pressJoinButton:withArg1:

if it had 3 arguments it would be:

pressJoinButton:withArg1:withArg2:

etc

Hope this helps!