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    "iPadOS: 18.0.0 -"
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  "documentType" : "symbol",
  "framework" : "ContactProvider",
  "identifier" : "/documentation/ContactProvider/ContactItemChangeObserver",
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  "title" : "ContactItemChangeObserver"
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# ContactItemChangeObserver

A protocol that defines a system observer that receives a resumable enumeration of changed contact items.

```
protocol ContactItemChangeObserver
```

## Overview

Your implementation of [`enumerateChanges(startingAt:for:)`](/documentation/ContactProvider/ContactItemEnumerator/enumerateChanges(startingAt:for:)) receives an observer that conforms to this type.
As you enumerate over your contacts, you provide them to the observer with the [`didUpdate(_:)`](/documentation/ContactProvider/ContactItemChangeObserver/didUpdate(_:)) and [`didDelete(_:)`](/documentation/ContactProvider/ContactItemChangeObserver/didDelete(_:)) methods.

## Topics

### Providing change data

[`didUpdate(_:)`](/documentation/ContactProvider/ContactItemChangeObserver/didUpdate(_:))

Provides an array of new and updated contact items to the observer.

[`ContactItem`](/documentation/ContactProvider/ContactItem)

An item in the contact database.

[`didDelete(_:)`](/documentation/ContactProvider/ContactItemChangeObserver/didDelete(_:))

Provides an array of deleted contact item identifiers to the observer.

[`Identifier`](/documentation/ContactProvider/ContactItem/Identifier)

The app’s identifier for an item in the contact database.

### Ending enumeration

[`didFinishEnumeratingChanges(upTo:moreComing:)`](/documentation/ContactProvider/ContactItemChangeObserver/didFinishEnumeratingChanges(upTo:moreComing:))

Marks a sync anchor of changed contact items as completed.

[`ContactItemSyncAnchor`](/documentation/ContactProvider/ContactItemSyncAnchor)

A snapshot point into enumerating changed contact items.

[`didFinishEnumeratingChangesWithError(_:)`](/documentation/ContactProvider/ContactItemChangeObserver/didFinishEnumeratingChangesWithError(_:))

Finishes the change enumeration with an error, indicating failure, to the observer.

### Optimizing observer batching

[`suggestedBatchSize`](/documentation/ContactProvider/ContactItemChangeObserver/suggestedBatchSize)

Retrieves the suggested number of changed contact items to include in a batch.


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