<!--
{
  "availability" : [
    "iOS: -",
    "iPadOS: -",
    "macCatalyst: -",
    "macOS: -",
    "tvOS: -",
    "visionOS: -",
    "watchOS: -"
  ],
  "documentType" : "symbol",
  "framework" : "CoreFoundation",
  "identifier" : "/documentation/CoreFoundation/CFBagHashCallBack",
  "metadataVersion" : "0.1.0",
  "role" : "Type Alias",
  "symbol" : {
    "kind" : "Type Alias",
    "modules" : [
      "Core Foundation"
    ],
    "preciseIdentifier" : "c:@T@CFBagHashCallBack"
  },
  "title" : "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.

```
typealias CFBagHashCallBack = (UnsafeRawPointer?) -> CFHashCode
```

## Parameters

`value`

The value used to compute the hash code.

## Return Value

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

## Discussion

This callback is passed to [`CFBagCreate(_:_:_:_:)`](/documentation/CoreFoundation/CFBagCreate(_:_:_:_:)) in a [`CFBagCallBacks`](/documentation/CoreFoundation/CFBagCallBacks) structure.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)