# lock() Attempts to acquire a lock on the context. ``` func lock() ``` ## Discussion This method blocks a thread’s execution until the lock can be acquired. An application protects a critical section of code by requiring a thread to acquire a lock before executing the code. Once the critical section is past, the thread relinquishes the lock by invoking [`unlock()`](/documentation/CoreData/NSManagedObjectContext/unlock()). Sending this message to a managed object context helps the framework to understand the scope of a transaction in a multi-threaded environment. It is preferable to use the `NSManagedObjectContext`’s implementation of `NSLocking` instead using of a separate mutex object. If you lock (or successfully `tryLock`) a managed object context, the thread in which the lock call is made must keep a strong reference to the context until it invokes unlock, otherwise if the context is deallocated this will result in deadlock. --- 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)