<!--
{
  "availability" : [
    "iOS: -",
    "iPadOS: -",
    "macCatalyst: -",
    "macOS: -",
    "tvOS: -",
    "visionOS: -",
    "watchOS: -"
  ],
  "documentType" : "symbol",
  "framework" : "CoreFoundation",
  "identifier" : "/documentation/CoreFoundation/CFCharacterSetCreateMutableCopy(_:_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Function",
  "symbol" : {
    "kind" : "Function",
    "modules" : [
      "Core Foundation"
    ],
    "preciseIdentifier" : "c:@F@CFCharacterSetCreateMutableCopy"
  },
  "title" : "CFCharacterSetCreateMutableCopy(_:_:)"
}
-->

# CFCharacterSetCreateMutableCopy(_:_:)

Creates a new mutable character set with the values from another character set.

```
func CFCharacterSetCreateMutableCopy(_ alloc: CFAllocator!, _ theSet: CFCharacterSet!) -> CFMutableCharacterSet!
```

## Parameters

`alloc`

The allocator to use to allocate memory for the new object. Pass `NULL` or kCFAllocatorDefault to use the current default allocator.

`theSet`

The character set to copy.

## Return Value

A new mutable character set containing the same characters as `theSet`. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029).

## Discussion

---

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)