Waiting for multiple GCD blocks to finish

GCD Waiting

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t group = dispatch_group_create();
 
// Add a task to the group
dispatch_group_async(group, queue, ^{
   // Some asynchronous work
});
 
// Do some other work while the tasks execute.
 
// When you cannot make any more forward progress,
// wait on the group to block the current thread.
dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
 
// Release the group when it is no longer needed.
dispatch_release(group);