---
title: notAKeyMarker
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsmaptablekeycallbacks/notakeymarker
---

# notAKeyMarker

No key put in map table can be this value. An exception is raised if attempt is made to use this value as a key

## Declaration

```swift
var notAKeyMarker: UnsafeRawPointer?
```