ios - How to Custom group notify for blocks of functions -

asynchronous block called in function, add these multiple functions group,process results of blocks when block execute completely.is there common , smart method implement?
dispatch_group_notify ,completionblock

dispatch_group_t _blocktaskgroup; .....  if (!_blocktaskgroup) {     _blocktaskgroup = dispatch_group_create(); }  dispatch_group_notify(_blocktaskgroup, dispatch_get_global_queue(dispatch_queue_priority_background, 0), ^{     nslog(@"finally!"); });  ....  dispatch_group_enter(_blocktaskgroup); [xxxxx computeinbackground:xx completion:^{     nslog(@"1 done");     dispatch_group_leave(group); }]; // dispatch_group_enter(_blocktaskgroup); [xxxxx computeinbackground:xx completion:^{     nslog(@"2 done");     dispatch_group_leave(_blocktaskgroup); }]; // dispatch_group_enter(_blocktaskgroup); [xxxxx computeinbackground:xx completion:^{     nslog(@"3 done");     dispatch_group_leave(_blocktaskgroup); }];