classes.nib

This is a very good sample source code on Mac. It shows how to customize the NSSavePanel

{
    IBClasses = (
        {CLASS = FirstResponder; LANGUAGE = ObjC; SUPERCLASS = NSObject; }, 
        {
            ACTIONS = {filePackagesAsDirAction = id; }; 
            CLASS = MyDocument; 
            LANGUAGE = ObjC; 
            OUTLETS = {
                appendCheck = NSButton; 
                navigatePackages = NSButton; 
                saveDialogCustomView = NSView; 
                soundOnCheck = NSButton; 
                textView = id; 
            }; 
            SUPERCLASS = NSDocument; 
        }, 
        {CLASS = MySound; LANGUAGE = ObjC; SUPERCLASS = Sound; }
    ); 
    IBVersion = 1; 
}