Uli's 10:23 AM Law
When the compiler gives you an error message like:
2007-08-12 09:57:42.893 MyApp *** +[MyAppView setArgumentOne:]: selector not recognized
And you know that your objects respond to that message, you dork overlooked the "+" at the start. You moron, you are calling an instance method on the class! If you got this object from an NSDictionary or NSArray, you dim-wit probably somewhere mistyped and stuffed the class into the collection, instead of the object.
In ObjC, classes are objects, too. Even when you don't want them to be. So watch your typing when you're refactoring code and a class list becomes an instance list, and watch what you put in a collection.