MustOverride
MustOverride provides a macro that you can use to ensure that a method of an abstract base class must be overriden by its subclasses.
Apple does not currently provide a way to flag this at compile time, and the standard approach of raising an exception in the base class’s implementation has two disadvantages: 1) it means that the method will only crash when it is called, which might only happen under difficult-to-reproduce conditions, and 2) you cannot provide a base implementation and require that the subclass calls super.
MustOverride uses some runtime magic to scan the class list at load time, and will crash immediately when the app is launched if the method is not implemented, even if it is never called.
