---
title: didChangeNotification
framework: Core ML
role: symbol
role_heading: Type Property
platforms: [iOS 14.0+, iPadOS 14.0+, Mac Catalyst 14.0+, visionOS 1.0+]
path: coreml/mlmodelcollection/didchangenotification
---

# didChangeNotification

The notification the framework sends when it receives an update to a model collection.

## Declaration

```swift
class let didChangeNotification: NSNotification.Name
```

## Discussion

Discussion Register your app to get notifications when a model collection update is available by calling addObserver(forName:object:queue:using:). let center = NotificationCenter.default var token: NSObjectProtocol?

token = center.addObserver(forName: MLModelCollection.didChangeNotification,                            object: nil,                            queue: nil) { [unowned self] note in     guard let modelCollection = note.object as? MLModelCollection else {         print("Model Collection notification's object is not a model collection")         return     }

// Use updated model collection ...     self.receivedUpdatedModelCollection(modelCollection)

// Clean up notification registration.     center.removeObserver(token!) } Typically, you register for model collection notifications when your app needs to use the newest models as soon as the collection is available. Your app can always get the newest model collection by calling beginAccessingModelCollectionWithIdentifier:completionHandler:.