multithreading - How to wait for a thread to finish in Objective-C -

i'm trying use method class downloaded somewhere. method executes in background while program execution continues. not want allow program execution continue until method finishes. how do that?

here's way using gcd:

  - (void)main {     [self dostuffinoperations]; }  - (void)dostuffingcd {     dispatch_group_t d_group = dispatch_group_create();     dispatch_queue_t bg_queue = dispatch_get_global_queue(dispatch_queue_priority_default, 0);      dispatch_group_async(d_group, bg_queue, ^{         [self dosomething:@"a"];     });      dispatch_group_async(d_group, bg_queue, ^{         [self dosomething:@"b"];     });      dispatch_group_async(d_group, bg_queue, ^{         [self dosomething:@"c"];     });       // can synchronously wait on current thread:     dispatch_group_wait(d_group, dispatch_time_forever);     dispatch_release(d_group);     nslog(@"all background tasks done!!");       // ****  or  ****      // if want happen after done:     dispatch_group_notify(d_group, dispatch_get_main_queue(), ^{         dispatch_release(d_group);         nslog(@"all background tasks done!!");             }); }  - (void)dosomething:(id)arg {     // whatever want arg here  }