In Apple's The Objective-C Programming Language: Defining a Class the section named "Redifining self" recommends that that class methods allocate and return instances use 'self' only to allocate an instance and then refer only to that instance. Thus, I have a number of subclasses, that have class methods along the lines of:

+ (id)scrollViewWithFrame: (NSRect)rectFrame
{
    id newInstance = [[[self alloc] initWithFrame:rectFrame] autorelease];
    [newInstance setHasHorizontalScroller: YES];
    [newInstance setHasVerticalScroller: YES];
    [newInstance setBorderType: NSNoBorder];
    [newInstance setAutoresizingMask: (NSViewWidthSizable
                | NSViewHeightSizable)];

    return newInstance;
}

The above is, of course, a subclass of NSScrollView. Unfortunately, Xcode 3.x all these NSView subclasses now raise warnings: "Warning: Multiple methods named '-setAutoresizingMask' found". I believe it has something to do with GCC 4.2, the settings of which I have not changed.

The warning is correct, of course, since NSView and its various subclasses all implement setAutoresizingMask, but it is also unnecessary. Since they're only warnings, I ignore them but there is a risk that in between the thirty or so unnecessary ones, a really useful warning lurks which I simply don't see. So, what to do? I do want to adhere to good coding practices and I want to build warning-free apps -- how can I do both?