How to use dispatch_async, dispatch_sync in Objective-C?

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Tarun Kumar · Answer

If you want to execute any specific task before any specific operation then use it between the dispatch_sync block. The code written in the dispatch_sync block will execute first because dispatch_sync() function creates a simple deadlock, as the currently executing block will waits for the next block to complete but the next block will not start until the currently running block completes.and the dispatch_async block will execute with default queue of your application main queue for example if we are downloading a file form the network and want to display updating in progress bar of downloads.Example of dispatch_async() function:dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void)
{
    // this is the background thread
    dispatch_async(dispatch_get_main_queue(), ^(void){
        // here you can display the updates of the progress bar
    });
});I hope the the above explanation is sufficient.

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How to use dispatch_async, dispatch_sync in Objective-C?

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