---
title: kCFCopyStringDictionaryKeyCallBacks
framework: corefoundation
role: symbol
role_heading: Global Variable
path: corefoundation/kcfcopystringdictionarykeycallbacks
---

# kCFCopyStringDictionaryKeyCallBacks

Predefined 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.

## Declaration

```swift
let kCFCopyStringDictionaryKeyCallBacks: CFDictionaryKeyCallBacks
```

## Discussion

Discussion You typically use a pointer to this constant when creating a new dictionary. important: For performance reasons, the default kCFCopyStringDictionaryKeyCallBacks behavior uses CFEqual(_:_:) which does not normalize the strings. This means that, for example, it does not consider CFStrings to be equal when they are the same but one is in pre-composed form (say, originating from a UTF-16 text file) and the other in decomposed form (say, originating from a file name). In cases where you use strings from different sources, you may want to pre-normalize the keys or else use a different set of functions to perform the comparison.

## See Also

### Constants

- [kCFTypeDictionaryKeyCallBacks](corefoundation/kcftypedictionarykeycallbacks.md)
- [kCFTypeDictionaryValueCallBacks](corefoundation/kcftypedictionaryvaluecallbacks.md)