---
title: CFDictionaryHashCallBack
framework: corefoundation
role: symbol
role_heading: Type Alias
path: corefoundation/cfdictionaryhashcallback
---

# CFDictionaryHashCallBack

Prototype of a callback function invoked to compute a hash code for a key. Hash codes are used when key-value pairs are accessed, added, or removed from a collection.

## Declaration

```swift
typealias CFDictionaryHashCallBack = (UnsafeRawPointer?) -> CFHashCode
```

## Parameters

- `value`: The value used to compute the hash code.

## Return Value

Return Value An integer that can be used as a table address in a hash table structure.

## Discussion

Discussion This callback is passed to CFDictionaryCreate(_:_:_:_:_:_:) in a CFDictionaryKeyCallBacks structure.

## See Also

### Callbacks

- [CFDictionaryApplierFunction](corefoundation/cfdictionaryapplierfunction.md)
- [CFDictionaryCopyDescriptionCallBack](corefoundation/cfdictionarycopydescriptioncallback.md)
- [CFDictionaryEqualCallBack](corefoundation/cfdictionaryequalcallback.md)
- [CFDictionaryReleaseCallBack](corefoundation/cfdictionaryreleasecallback.md)
- [CFDictionaryRetainCallBack](corefoundation/cfdictionaryretaincallback.md)