When using associated objects, an Objective-C runtime feature available starting from iOS 4 and OSX 10.6, it's necessary to define a key for storing and retrieving the object at runtime.

The typical usage is defining the key like follows

static char const * const ObjectTagKey = "ObjectTag";

and then use is to store the object

objc_setAssociatedObject(self, ObjectTagKey, newObjectTag, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

and retrieve it

objc_getAssociatedObject(self, ObjectTagKey);

(example taken by http://oleb.net/blog/2011/05/faking-ivars-in-objc-categories-with-associative-references/)

Is there a cleaner way to define the associated object key, that doesn't involve the declaration of extra variables?

objective-c objective-c-runtime associated-object
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