When to use a colon with a @selector

Question

Just getting going with iPhone development and Objective-C.

Yesterday I was trying to addObserver for a notification in a view of mine, and I kept getti

Answer 1

You seem to be missing one concept here: colon is, in some way, a part of the method name. E.g., method

-(IBAction) doIt:(id)sender;

has name doIt:. Thus, colon should be used to reference this method.
But this method doesn't have a colon at the end

-(IBAction) doItWithoutParameter;

Same goes for methods accepting multiple arguments, they have names like doItWithParam1:andParam2: