Will Objective-C runtime release retained associative references for user?

问题

When some codes like this:

objc_setAssociatedObject (
  obj,
  &key,
  val,
  OBJC_ASSOCIATION_RETAIN
);

Do I need to call related

objc_setAssociatedObject (
  obj,
  &key,
  nil,
  OBJC_ASSOCIATION_RETAIN
);

to release the retained value? Does Objective-C runtime auto release the associative references in dealloc or somewhere?

回答1:

Associated objects will be released when the parent object is deallocated. See the documentation here, specifically this example:

At point 1, the string overview is still valid because the OBJC_ASSOCIATION_RETAIN policy specifies that the array retains the associated object. When the array is deallocated, however (at point 2), overview is released and so in this case also deallocated.

来源：https://stackoverflow.com/questions/6122600/will-objective-c-runtime-release-retained-associative-references-for-user