Debugging selectors in Xcode

I'm trying to debugg my iphone app, it uses selectors as method-parameter "didFinishSelector:" When i do step over my method or step into in xcode, it goes over my method forward. Some time later, my method finishes it's work, and .. it has to go into my selector function and i want to see it in Xcode.

How is this signal mechanism is designed ? Something like classic C forks or else multi-threads开发者_如何学编程 ? Is it possible to view it during visual debugging ? If yes, then how ?

    //create and authenticate to a google spreadsheet service 
    GDataServiceGoogleSpreadsheet *service = [ self spreadsheetService ];
    NSURL *feedURL = [ NSURL URLWithString: kGDataGoogleSpreadsheetsPrivateFullFeed ];

    //check autentication success ( invoke "googleTicket" method for debug success & error )
    [ service authenticateWithDelegate: self
               didAuthenticateSelector: @selector( googleTicket: authenticatedWithError: ) ];

    //fetch retrieves the feed of spreadsheets entries 
    GDataServiceTicket *ticket;
    ticket = [ service fetchFeedWithURL: feedURL
                               delegate: self
                     didFinishSelector: @selector( spreadsheetsTicket: finishedWithFeed: error: ) ];

Here's an example. When i'm debugging, i call step-over, step-over, debugger goes through method [service authenticateWithDelage: didAuthenticateSelector:], it goes directly to [service fetchFeedWithURL: delegate: didFinishSelector:] and after that it goes forward. But i want to see, when this two methods do finish, and i want to see how it goes into my selectors "googleTicket: authenticateWithError" and "spreadsheetsTicket: finishedWithFeed: error:"