Best way of preventing other programmers from calling -init

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

Answer 1

The syntax has been shortened to just:

- (instancetype)init NS_UNAVAILABLE;

Answer 2

initWith:Stuff and:OtherStuff should never be more than convenience constructors.

In that they effectively should call

self = [self init];

if(self)
{
    self.stuff = Stuff;
    self.other = OtherStuff;
}

so [object init] will always return an object in a predefined state, and [object initWithStuff:stuff] will return the object in the predefined state with stuff overridden.

Basically what I'm getting at is, its bad practice to discourage [object init] especially when someone subclasses your subclass in the future….

Answer 3

Flag it deprecated? Developers will be developers, you can't stop us all! ;-)

How do I flag a method as deprecated in Objective-C 2.0?

Answer 4

To add to what @DarkDust posted, you could alternatively use UNAVAILABLE_ATTRIBUTE

- (id)init UNAVAILABLE_ATTRIBUTE;

This will throw an error when a user tries to call init on an instance of this class.

Answer 5

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.