Question

When designing a class hierarchy, sometimes the subclass has added a new initWithSomeNewParam method, and it would be desirable to disable calls to the old init method inherited from the superclass.

First of all, I’ve read the question here, where the proposed alternatives are either override init to throw an exception at runtime, or override and set default values for properties. In my case, I don’t wan’t to provide default values, and I want to clearly indicate that the old method should not be called, and instead the new method with parameters should be used.

So the runtime exception are fine, but unless the code is debugged, there’s no way for other programmers in the team to notice that the old method is no longer intended to be used.

If I’m correct, there’s no way to mark a method as “private”. So, apart from adding comments, is there a way to do this?

Thanks in advance.

Answer 1

You can explicitly mark your init as being unavailable in your header file:

- (id) init __unavailable;

or:

- (id) init __attribute__((unavailable));

With the later syntax, you can even give a reason:

- (id) init __attribute__((unavailable("Must use initWithFoo: instead.")));

The compiler then issues an error (not a warning) if someone tries to call it.