Sometimes you don’t want to support init, or another method. How best do you do it?

In the old days you would be to catch it in runtime; call [self release], error, then return nil. This approach should no longer be used. It leaves a ticking timebomb waiting for somebody, quite possibly a later version of yourself, to call it and blow everything up.

Since macOS 10.7 and iOS 5 NSObjCRuntime.h has included NS_UNAVAILABLE. An easy to use macro wrapper of the unavailable __attribute__. This is great as it provides a compile time error when the method is used, preventing any issue from ever even reaching runtime.

@interface SomeClass : NSObject
// ...
- (instancetype)init NS_UNAVAILABLE;
// ...
@end

More generally, you can use this to cause a compile error for any method you need it to.

Swift

Apple has also conveniently added NS_SWIFT_UNAVAILABLE to allow you to disable Objective-C methods in Swift.

License

Any source in this article is released under the ISC License.