---
title: CFNull
framework: corefoundation
role: symbol
role_heading: Class
path: corefoundation/cfnull
---

# CFNull

## Declaration

```swift
class CFNull
```

## Overview

Overview The CFNull opaque type defines a unique object used to represent null values in collection objects (which don’t allow NULL values). CFNull objects are neither created nor destroyed. Instead, a single CFNull constant object—kCFNull—is defined and is used wherever a null value is needed. The CFNull opaque type is available in macOS 10.2 and later.

## Topics

### CFNull Miscellaneous Functions

- [CFNullGetTypeID()](corefoundation/cfnullgettypeid().md)

### Constants

- [Predefined Value](corefoundation/predefined-value.md)

## Relationships

### Conforms To

- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)

## See Also

### Related Documentation

- [Collections Programming Topics for Core Foundation](apple-archive/documentation/CoreFoundation/Conceptual/CFCollections.md)

### Opaque Types

- [CFAllocator](corefoundation/cfallocator.md)
- [CFArray](corefoundation/cfarray.md)
- [CFAttributedString](corefoundation/cfattributedstring.md)
- [CFBag](corefoundation/cfbag.md)
- [CFBinaryHeap](corefoundation/cfbinaryheap.md)
- [CFBitVector](corefoundation/cfbitvector.md)
- [CFBoolean](corefoundation/cfboolean.md)
- [CFBundle](corefoundation/cfbundle.md)
- [CFCalendar](corefoundation/cfcalendar.md)
- [CFCharacterSet](corefoundation/cfcharacterset.md)
- [CFData](corefoundation/cfdata.md)
- [CFDate](corefoundation/cfdate.md)
- [CFDateFormatter](corefoundation/cfdateformatter.md)
- [CFDictionary](corefoundation/cfdictionary.md)
- [CFError](corefoundation/cferror.md)