Function

dispatch_sync

Submits a block object for execution on a dispatch queue and waits until that block completes.

Declaration

void dispatch_sync(dispatch_queue_t queue, dispatch_block_t block);

Parameters

queue

The queue on which to submit the block. This parameter cannot be NULL.

block

The block to be invoked on the target dispatch queue. This parameter cannot be NULL.

Discussion

Submits a block to a 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 an optimization, this function invokes the block on the current thread when possible.