---
title: UnaryFileSystemExtension
framework: fskit
role: symbol
role_heading: Protocol
path: fskit/unaryfilesystemextension
---

# UnaryFileSystemExtension

A protocol for implementing a minimal file system as an app extension.

## Declaration

```swift
protocol UnaryFileSystemExtension : AppExtension
```

## Overview

Overview Your app needs to do the following to implement a FSKit-compatible minimal file system: Create a subclass of FSUnaryFileSystem, which also conforms to FSUnaryFileSystemOperations. Implement a @main struct that conforms to the UnaryFileSystemExtension protocol. Your implementation of this protocol returns the type of class from step 1 as its FileSystem associated type, and returns an instance of it as the fileSystem property.

## Topics

### Declaring the implemented file system

- [fileSystem](fskit/unaryfilesystemextension/filesystem-swift.property.md)
- [FileSystem](fskit/unaryfilesystemextension/filesystem-swift.associatedtype.md)

## Relationships

### Inherits From

- [AppExtension](extensionfoundation/appextension.md)