---
title: CFBagHashCallBack
framework: corefoundation
role: symbol
role_heading: Type Alias
path: corefoundation/cfbaghashcallback
---

# CFBagHashCallBack

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

## Declaration

```swift
typealias CFBagHashCallBack = (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 CFBagCreate(_:_:_:_:) in a CFBagCallBacks structure.

## See Also

### Callbacks

- [CFBagApplierFunction](corefoundation/cfbagapplierfunction.md)
- [CFBagCopyDescriptionCallBack](corefoundation/cfbagcopydescriptioncallback.md)
- [CFBagEqualCallBack](corefoundation/cfbagequalcallback.md)
- [CFBagReleaseCallBack](corefoundation/cfbagreleasecallback.md)
- [CFBagRetainCallBack](corefoundation/cfbagretaincallback.md)