objective c - How to deprecate a method in Xcode

Question

We have our library we ship to our customers, and I'd like to mark some methods as "deprecated" because we changed them (like Apple does in the iPhone SDK).

I've seen the __OSX_AVAILABLE_BUT_DEPRECATED pre-processor macro, which is mapped to __AVAILABILITY_INTERNAL, which is mapped to __attribute__((deprecated))...

Well i'm a bit confused with this stuff!

Anybody knows something about that ?

Answer 1

__attribute__((deprecated)) is the gcc way (also supported in clang) of marking a function / method as deprecated. When one is marked as "deprecated", a warning will be produced whenever anyone calls it.

The syntax for normal functions would be

__attribute__((deprecated))
void f(...) {
  ...
}

// gcc 4.5+ / clang
__attribute__((deprecated("g has been deprecated please use g2 instead")))
void g(...) {
  ...
}

and that of Objective-C methods would be

@interface MyClass : NSObject { ... }
-(void)f:(id)x __attribute__((deprecated));
...
@end

You can also mark the whole class as deprecated with

__attribute__((deprecated))
@interface DeprecatedClass : NSObject { ... }
...
@end

---

Apple also provides the <AvailabilityMacros.h> header which provides the DEPRECATED_ATTRIBUTE and DEPRECATED_MSG_ATTRIBUTE(msg) macros that expand to the above attributes, or nothing if the compiler doesn't support attributes. Note that this header doesn't exist outside of OS X / iOS.

---

Side note, if you are using Swift you use the @available attribute to deprecate an item, e.g.

@available(*, deprecated=2.0, message="no longer needed")
func f() {
    ...
}