sync(execute:)
Submits a block object for execution and returns after that block finishes executing.
Declaration
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
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.