The callback used to retain each value as they are added to the collection. This callback returns the value to use as the value 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 value. If
NULL, values are not retained. See
CFDictionary for a descriptions of this function’s parameters.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
- Core Foundation