ios - Objective-C: Wait to execute 'While' loop until NSURLConnection request is complete -

basically want way issue nsurlrequest multiple times in loop until condition has been met. using rest api rest api allows maximum of 1,000 results @ time. if have, lets 1,500 total, want make request first 1,000 need rest exact request , except startat: parameter different(so go 1001 - 1500. want set in while loop(while done loading data) , reading semaphores not working out expected to. don't know how many results have until make first request. 50, 1000, or 10,000.

here code:

while(!finishedloadingalldata){         dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);          nsurlrequest *myrequest = [self loaddata: startat:startat maxresults:maxresults];          [nsurlconnection sendasynchronousrequest:myrequest                                            queue:[nsoperationqueue mainqueue]                                completionhandler:^(nsurlresponse *response, nsdata *data, nserror *error) {                                     if(error){                                        completionhandler(issueswithprojectdata, error);                                    }                                    else{                                        nsdictionary *issuesdictionary = [[nsdictionary alloc] initwithdictionary:[nsjsonserialization jsonobjectwithdata:data options:nsjsonreadingmutablecontainers error:&error]];                                        [issueswithprojectdata addobjectsfromarray:issuesdictionary[@"issues"]];                                         if(issueswithprojectdata.count == [issuesdictionary[@"total"] integervalue]){                                            completionhandler([issueswithprojectdata copy], error);                                             finishedloadingalldata = yes;                                        }                                        else{                                            startat = maxresults + 1;                                            maxresults = maxresults + 1000;                                        }                                    }                                    dispatch_semaphore_signal(semaphore);                                }];          dispatch_semaphore_wait(semaphore, dispatch_time_forever);     } 

basically want keep while loop waiting until completion block finished. , want while loop check if have of data or not(and if not, make request updated startat value/maxresults value.

right hangs on dispatch_semaphore_wait(semaphore, dispatch_time_forever);

what doing wrong or need do? maybe semaphores wrong solution. thanks.

ok. more look, more don't think bad idea have semaphores solve problem, since other way have serial queue, etc. , solution isn't more complicated.
problem is, requesting completion handler run on main thread

[nsurlconnection sendasynchronousrequest:myrequest                                        queue:[nsoperationqueue mainqueue]                            completionhandler:^(nsurlresponse *response, nsdata *data, nserror *error)  

and creating nsurl request in main thread. hence while waits semaphore released on mainthread, nsurl completion handler waiting mainthread free of current run loop.

create new operation queue.