# performAndWait(_:) Submits a closure to the context’s queue for synchronous execution. ``` @preconcurrency nonisolated func performAndWait(_ block: @Sendable () throws -> T) rethrows -> T ``` ## Parameters `block` The closure to perform. ## Discussion This method supports *reentrancy* — meaning it’s safe to call the method again, from within the closure, before the previous invocation completes. --- 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)