---
title: NSFileProviderDomainVersion
framework: fileprovider
role: symbol
role_heading: Class
path: fileprovider/nsfileproviderdomainversion
---

# NSFileProviderDomainVersion

An opaque object that identifies a specific version of a domain.

## Declaration

```swift
class NSFileProviderDomainVersion
```

## Overview

Overview The file provider extension is responsible for assigning and updating the domain version. To specify the domain version, adopt the NSFileProviderDomainState protocol. The system then calls your extension’s domainVersion method to read the current version. The system reads the domain version after you call: The createItem(basedOn:fields:contents:options:request:completionHandler:) completion handler The modifyItem(_:baseVersion:changedFields:contents:options:request:completionHandler:) completion handler The deleteItem(identifier:baseVersion:options:request:completionHandler:) completion handler The item(for:request:completionHandler:) completion handler The finishEnumerating(upTo:) or finishEnumeratingWithError(_:) method when enumerating the materialized set. The system always reads the domain version on the same dispatch queue as the completion handler. Your extension defines when the domain version changes. When you update the version, call the signalEnumerator(for:completionHandler:) and passing the workingSet constant as the containerItemIdentifier property. This notifies the system of the update. The system ignores any lower versions. When the system discovers a change on disk, it associates that change with the current domain version. It then includes the version in the NSFileProviderRequest object passed to the file provider extension. Only file provider extensions based on the NSFileProviderReplicatedExtension use instances of this class. Each version object is immutable. You can use them as keys in a dictionary.

## Topics

### Creating Versions

- [next()](fileprovider/nsfileproviderdomainversion/next().md)

### Initializers

- [init(coder:)](fileprovider/nsfileproviderdomainversion/init(coder:).md)

## Relationships

### Inherits From

- [NSObject](objectivec/nsobject-swift.class.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [Comparable](swift/comparable.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCoding](foundation/nscoding.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)
- [NSSecureCoding](foundation/nssecurecoding.md)

## See Also

### Domains

- [NSFileProviderDomainState](fileprovider/nsfileproviderdomainstate.md)