dispatch_async and block in iOS

ios dispatch-async
Tunvir Rahman Tusher picture Tunvir Rahman Tusher · May 16, 2013 · Viewed 68.5k times · Source

What this piece of code mean?

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        TMBaseParser *parser=[[TMBaseParser alloc] init];
        parser.delegate=self;
        NSString *post =nil;
        NSData *postData = [post dataUsingEncoding:NSUTF8StringEncoding];
        [parser parseForServiceType:TMServiceCategories postdata:postData];
    });

please explain it briefly.

Answer

Marcin Kuptel picture Marcin Kuptel · May 16, 2013

The piece of code in

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

});

is run asynchronously on a background thread. This is done because parsing data may be a time consuming task and it could block the main thread which would stop all animations and the application wouldn't be responsive.

If you want to find out more, read Apple's documentation on Grand Central Dispatch and Dispatch Queue.

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