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# CFNull

```
class CFNull
```

## 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`](/documentation/CoreFoundation/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()`](/documentation/CoreFoundation/CFNullGetTypeID())

Returns the type identifier for the CFNull opaque type.

### Constants

[Predefined Value](/documentation/CoreFoundation/predefined-value)

Predefined CFNull object.

## See Also

  [Collections Programming Topics for Core Foundation](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFCollections/CFCollections.html#//apple_ref/doc/uid/10000124i)


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