---
title: "sync(execute:)"
framework: dispatch
role: symbol
role_heading: Instance Method
path: "dispatch/dispatchqueue/sync(execute:)-3segw"
---

# sync(execute:)

Submits a block object for execution and returns after that block finishes executing.

## Declaration

```swift
func sync(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

Discussion This function submits a block to the specified dispatch queue for synchronous execution. Unlike dispatch_async, this function does not return until the block has finished. Calling this function and targeting the current queue results in deadlock. Unlike with 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. As a performance optimization, this function executes blocks on the current thread whenever possible, with one exception: Blocks submitted to the main dispatch queue always run on the main thread.

## See Also

### Executing Tasks Synchronously

- [sync(execute:)](dispatch/dispatchqueue/sync(execute:)-2fzvo.md)
- [sync(execute:)](dispatch/dispatchqueue/sync(execute:)-20xby.md)
- [sync(flags:execute:)](dispatch/dispatchqueue/sync(flags:execute:).md)
- [asyncAndWait(execute:)](dispatch/dispatchqueue/asyncandwait(execute:)-1udeu.md)