# createAudioUnit(with:) Creates an instance of an extension’s audio unit. ``` func createAudioUnit(with desc: AudioComponentDescription) throws -> AUAudioUnit ``` ## Parameters `desc` The description of the audio component. ## Return Value An instance of the extension’s audio unit. ## Discussion This method is called only once per factory instance. > Note: > In non-ARC code, “create” methods return unretained objects (unlike C “create” functions). In this scenario, you should return an object with a reference count of 1, but autoreleased. > Handling Errors in Swift: > In Swift, this method returns a nonoptional result and is marked with the `throws` keyword to indicate that it throws an error in cases of failure. > > You call this method in a `try` expression and handle any errors in the `catch` clauses of a `do` statement, as described in [Error Handling](https://docs.swift.org/swift-book/LanguageGuide/ErrorHandling.html) in [The Swift Programming Language](https://docs.swift.org/swift-book/) and `About Imported Cocoa Error Parameters`. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)