Submits a barrier block for asynchronous execution and returns immediately.


void dispatch_barrier_async(dispatch_queue_t queue, dispatch_block_t block);



The dispatch queue on which to execute the barrier block. The queue is retained by the system until the block has run to completion. This parameter cannot be NULL.


The barrier block to submit to the target dispatch queue. This block is copied and retained until it finishes executing, at which point it is released. This parameter cannot be NULL.


Calls to this function always return immediately after the block has been submitted and never wait for the block to be invoked. When the barrier block reaches the front of a private concurrent queue, it is not executed immediately. Instead, the queue waits until its currently executing blocks finish executing. At that point, the barrier block executes by itself. Any blocks submitted after the barrier block are not executed until the barrier block completes.

The queue you specify should be a concurrent queue that you create yourself using the dispatch_queue_create function. If the queue you pass to this function is a serial queue or one of the global concurrent queues, this function behaves like the dispatch_async function.

See Also

Creating a Barrier Asynchronously


Submits a barrier function for asynchronous execution and returns immediately.