Instance Property


The callback used to retain each key as they are added to the collection. This callback returns the value to use as the key in the dictionary, which is usually the value parameter passed to this callback, but may be a different value if a different value should be used as the key. If NULL, keys are not retained. See CFDictionaryRetainCallBack for a descriptions of this function’s parameters.


Beta Software

This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.

Learn more about using Apple's beta software