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# Predefined Callback Structures

CFDictionary provides some predefined callbacks for your convenience.

## Topics

### Constants

[`let kCFCopyStringDictionaryKeyCallBacks: CFDictionaryKeyCallBacks`](/documentation/CoreFoundation/kCFCopyStringDictionaryKeyCallBacks)

Predefined [`CFDictionaryKeyCallBacks`](/documentation/CoreFoundation/CFDictionaryKeyCallBacks) structure containing a set of callbacks appropriate for use when the keys of a CFDictionary are all CFString objects, which may be mutable and need to be copied in order to serve as constant keys for the values in the dictionary.

[`let kCFTypeDictionaryKeyCallBacks: CFDictionaryKeyCallBacks`](/documentation/CoreFoundation/kCFTypeDictionaryKeyCallBacks)

Predefined [`CFDictionaryKeyCallBacks`](/documentation/CoreFoundation/CFDictionaryKeyCallBacks) structure containing a set of callbacks appropriate for use when the keys of a CFDictionary are all CFType-derived objects.

[`let kCFTypeDictionaryValueCallBacks: CFDictionaryValueCallBacks`](/documentation/CoreFoundation/kCFTypeDictionaryValueCallBacks)

Predefined [`CFDictionaryValueCallBacks`](/documentation/CoreFoundation/CFDictionaryValueCallBacks) structure containing a set of callbacks appropriate for use when the values in a CFDictionary are all CFType-derived objects.


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