Run Disptach sync block from async

Question

I am new to Dispatch queue, now am trying to call background operations through this dispatch queue.

Here I have a doubt, please help me in this. In the below example,

whatQueue:- Should it be mainQueue, queueA or shall I create a new Queue?

dispatch_queue_t queueA = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(queueA, ^{
     NSMutableArray * items = listofItems;
    for(NSString * str in items)
    {
         //Run a sync block to send str to server
        dispatch_sync(***whatQueue***, ^{

        });
    }
});

Thanks, Phani

score 0 · Answer 1 · answered Jul 08 '12 at 06:36

0

Use dispatch_get_main_queue for nested dispatches (I assume you want a sync dispatch on the main thread for UI updates, after all). Otherwise, you're already operating in the background and no further dispatches are required.

answered Jul 08 '12 at 06:36

CodaFi

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score 0 · Accepted Answer · answered Jul 08 '12 at 06:55

You are not explaining too much as to the reasons why you want the inner block to be executed in a sync way. I assume that you want:

to serialize the sending of the strings to the server;
wait for all the strings to be sent before continuing.

In this case, you can:

execute the network task on the same queueA (no need for a new dispatch);
ensure that your underlying networking layer (NSURLConnection/AFNetworking/ASIHTTP/...) is doing a sync network operation (otherwise, the network request will return immediately and complete in the background in its own thread).

score 0 · Answer 3 · answered Jul 08 '12 at 06:58

thanks for your reply,

I don't want to update any thing on the UI just want push offline data to the server without effecting user interface.

So main dispatch queue iterates all the records and should send records synch mode using nested queue and each request's response should also handled.

Run Disptach sync block from async

3 Answers3