---
title: CNChangeHistoryEventVisitor
framework: contacts
role: symbol
role_heading: Protocol
path: contacts/cnchangehistoryeventvisitor
---

# CNChangeHistoryEventVisitor

An interface for receiving notice of changes to contacts and groups.

## Declaration

```swift
protocol CNChangeHistoryEventVisitor : NSObjectProtocol
```

## Overview

Overview Implement this protocol to receive events that describe when a user adds, updates, or deletes contacts or groups outside your app.

## Topics

### Updating contacts

- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-9w73y.md)
- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-1pf2a.md)
- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-ci4z.md)

### Updating groups

- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-ve62.md)
- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-23p9h.md)
- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-82duo.md)

### Updating subgroups

- [visitAddSubgroup(_:)](contacts/cnchangehistoryeventvisitor/visitaddsubgroup(_:).md)
- [visitRemoveSubgroup(_:)](contacts/cnchangehistoryeventvisitor/visitremovesubgroup(_:).md)

### Updating contacts in groups

- [visitAddMember(_:)](contacts/cnchangehistoryeventvisitor/visitaddmember(_:).md)
- [visitRemoveMember(_:)](contacts/cnchangehistoryeventvisitor/visitremovemember(_:).md)

### Resetting synced data

- [visit(_:)](contacts/cnchangehistoryeventvisitor/visit(_:)-2yhz3.md)

## Relationships

### Inherits From

- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Change history data

- [CNChangeHistoryAddContactEvent](contacts/cnchangehistoryaddcontactevent.md)
- [CNChangeHistoryAddGroupEvent](contacts/cnchangehistoryaddgroupevent.md)
- [CNChangeHistoryAddMemberToGroupEvent](contacts/cnchangehistoryaddmembertogroupevent.md)
- [CNChangeHistoryAddSubgroupToGroupEvent](contacts/cnchangehistoryaddsubgrouptogroupevent.md)
- [CNChangeHistoryDeleteContactEvent](contacts/cnchangehistorydeletecontactevent.md)
- [CNChangeHistoryDeleteGroupEvent](contacts/cnchangehistorydeletegroupevent.md)
- [CNChangeHistoryDropEverythingEvent](contacts/cnchangehistorydropeverythingevent.md)
- [CNChangeHistoryEvent](contacts/cnchangehistoryevent.md)
- [CNChangeHistoryFetchRequest](contacts/cnchangehistoryfetchrequest.md)
- [CNChangeHistoryRemoveMemberFromGroupEvent](contacts/cnchangehistoryremovememberfromgroupevent.md)
- [CNChangeHistoryRemoveSubgroupFromGroupEvent](contacts/cnchangehistoryremovesubgroupfromgroupevent.md)
- [CNChangeHistoryUpdateContactEvent](contacts/cnchangehistoryupdatecontactevent.md)
- [CNChangeHistoryUpdateGroupEvent](contacts/cnchangehistoryupdategroupevent.md)