# precondition(_:) Asserts if the lock object fails to meet specified ownership requirements. ``` func precondition(_ condition: OSAllocatedUnfairLock.Ownership) ``` ## Parameters `condition` The ownership status to check. ## Discussion Call this function to ensure the ownership state of the lock is what your code requires. For example, if you call this function and pass [`OSAllocatedUnfairLock.Ownership.owner`](/documentation/os/OSAllocatedUnfairLock/Ownership/owner), the app terminates if the object is locked, but the calling code doesn’t own the lock. Similarly, if you call it and pass [`OSAllocatedUnfairLock.Ownership.notOwner`](/documentation/os/OSAllocatedUnfairLock/Ownership/notOwner), the app terminates if the calling code doesn’t own the lock, or if the object isn’t locked. --- 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)