---
title: kindKey
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/nskeyvaluechangekey/kindkey
---

# kindKey

An NSNumber object that contains a value corresponding to one of the NSKeyValueChange enums, indicating what sort of change has occurred.

## Declaration

```swift
static let kindKey: NSKeyValueChangeKey
```

## Discussion

Discussion A value of NSKeyValueChange.setting indicates that the observed object has received a setValue(_:forKey:) message, or that the key-value-coding-compliant set method for the key has been invoked, or that one of the willChangeValue(forKey:) or didChangeValue(forKey:) methods has otherwise been invoked. A value of NSKeyValueChange.insertion, NSKeyValueChange.removal, or NSKeyValueChange.replacement indicates that mutating messages have been sent a key-value observing compliant collection proxy, or that one of the key-value-coding-compliant collection mutation methods for the key has been invoked, or a collection will change or did change method has been otherwise been invoked. You can use the uintValue method on the NSNumber object to retrieve the value of the change kind.

## See Also

### Type Properties

- [indexesKey](foundation/nskeyvaluechangekey/indexeskey.md)
- [newKey](foundation/nskeyvaluechangekey/newkey.md)
- [notificationIsPriorKey](foundation/nskeyvaluechangekey/notificationispriorkey.md)
- [oldKey](foundation/nskeyvaluechangekey/oldkey.md)