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# CNChangeHistoryEventVisitor

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

```
protocol CNChangeHistoryEventVisitor : NSObjectProtocol
```

## 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

[`-  visitAddContactEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-9w73y)

Tells the delegate that the user added a contact.

[`-  visitUpdateContactEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-1pf2a)

Tells the delegate that the user updated a contact.

[`-  visitDeleteContactEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-ci4z)

Tells the delegate that the user deleted a contact.

### Updating groups

[`-  visitAddGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-ve62)

Tells the delegate that the user added a group.

[`-  visitUpdateGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-23p9h)

Tells the delegate that the user updated a group.

[`-  visitDeleteGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-82duo)

Tells the delegate that the user deleted a group.

### Updating subgroups

[`-  visitAddSubgroupToGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visitAddSubgroup(_:))

Tells the delegate that the user added a subgroup to a group.

[`-  visitRemoveSubgroupFromGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visitRemoveSubgroup(_:))

Tells the delegate that the user removed a subgroup from a group.

### Updating contacts in groups

[`-  visitAddMemberToGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visitAddMember(_:))

Tells the delegate that the user added a contact to a group.

[`-  visitRemoveMemberFromGroupEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visitRemoveMember(_:))

Tells the delegate that the user removed a contact from a group.

### Resetting synced data

[`-  visitDropEverythingEvent:`](/documentation/Contacts/CNChangeHistoryEventVisitor/visit(_:)-2yhz3)

Tells the delegate to drop all contacts and groups before handling more events.

## Relationships

### Inherits From

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

---

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