# asyncAndWait(execute:) Submits a work item for execution and returns only after it finishes executing. ``` func asyncAndWait(execute block: () -> Void) ``` ## Parameters `block` The block that contains the work to perform. This block has no return value and no parameters. This parameter cannot be `NULL`. ## Discussion This function submits work to the specified queue for execution. Unlike [`dispatch_async`](/documentation/Dispatch/dispatch_async), this function does not return until after the block finishes. Calling this function and targeting the current queue results in deadlock. Unlike [`sync(execute:)`](/documentation/Dispatch/DispatchQueue/sync(execute:)-3segw), this function respects all attributes of the queue when it executes the block. For example, it respects the quality-of-service level and autorelease frequency of the target queue. If the runtime has already brought up a thread to service asynchronous work items, the system uses that same thread to execute any synchronous blocks you submitted using this function. If the runtime hasn’t brought up a thread to service asynchronous work items, the sytem executes these synchronous blocks on the current thread as an optimization. However, these optimizations apply only when `queue` targets a global concurrent queue. If it targets any other queue, the system executes the work on that queue’s thread. For example, if `queue` targets the main queue, the block always runs on the main thread. Unlike with [`dispatch_async`](/documentation/Dispatch/dispatch_async), no retain is performed on the target queue. Because calls to this function are synchronous, it “borrows” the reference of the caller. Moreover, no `Block_copy` is performed on the block. --- 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)