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# Predefined Callback Structures

CFBag provides some predefined callbacks for your convenience.

## Topics

### Constants

[`let kCFTypeBagCallBacks: CFBagCallBacks`](/documentation/CoreFoundation/kCFTypeBagCallBacks)

[`let kCFCopyStringBagCallBacks: CFBagCallBacks`](/documentation/CoreFoundation/kCFCopyStringBagCallBacks)

Predefined [`CFBagCallBacks`](/documentation/CoreFoundation/CFBagCallBacks) structure containing a set of callbacks appropriate for use when the values in a CFBag are all CFString objects. The bag makes immutable copies of the strings placed into it.


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