ios - Cancel PFQuery takes too much time to load -

apologies couldn't think of better way describe application’s functionality.

i've found quite lot of posts topic, in old archive @ parse.com. nevertheless doesn't work me. after creating instance of pfquery triggered pfquery.findobjects (but runs on background thread) i'm not able cancel during request process.

scenario : have app connects parse. have display data more 100 records in datadisplay screen , has button when user click on button , if pfquery.findobjects still run on background thread have cancel it.

i have tried inserting pfquery.cancel in viewwilldisappear, can not stop , due these datadisplay screen’s dealloc method not call.

my code, incase may help:

- (void)loadandsortingsonginformationws {  if(isinternet) {      if(self.isshowloadingforskipsong)//not showing activity indicator         self.isshowloadingforskipsong = no;      else if(self.isfirstload || self.isaddpulltorefreshlikesong)//showing indicator         [self showhideloading:yes];      pfquery *query = [pfquery querywithclassname:[userplaylistsongs parseclassname]];     [query setlimit:1000];     [query orderbydescending:@"createdat"];     [query wherekey:@"playlist" equalto:self.playlistinfo];     [query includekey:@"playlist"];     [query includekey:@"song"];     [query includekey:@"addedby"];     [query includekey:@"host"];      __weak typeof(self) weakself = self;      [self.opearation addoperationwithblock:^{          [query findobjectsinbackgroundwithblock:^(nsarray *objects, nserror *error) {              if (objects.count == 0) {//no songs found                  //if there no records                 dispatch_async(dispatch_get_main_queue(), ^{                      [weakself showhideloading:no];                      if(weakself.isfirstload || weakself.isaddpulltorefreshlikesong) {//problem while user pull refresh when there no song                          [kstoastview ks_showtoast:@"no songs found." duration:1.0f];                     }                 });             }              else {//songs found                  dispatch_async(dispatch_get_main_queue(), ^{                      nsmutablearray *arrparsesonglist = [[nsmutablearray alloc] init];                     __block nsinteger gettotalobjectscount = 0;                      for(nsinteger i=0; i<objects.count; i++) {                          songlistinfo *songlistdata = [[songlistinfo alloc] init];                         songlistdata.userplaylistinfo = objects[i];                          songlistdata.totlikes = [objects[i][@"likes"] integervalue];                         songlistdata.totdislikes = [objects[i][@"dislikes"] integervalue];                         songlistdata.isplaying = [objects[i][@"playingstatus"] boolvalue];                         songlistdata.songinfo = objects[i][@"song"];                         songlistdata.hostinfo = objects[i][@"host"];                         songlistdata.addedinfo = objects[i][@"addedby"];                         songlistdata.playlistinfo = objects[i][@"playlist"];                         songlistdata.alreadyplayedorder = [objects[i][@"alreadyplayedindex"] integervalue];                         songlistdata.totrating = songlistdata.totlikes - songlistdata.totdislikes;                         songlistdata.createddate = songlistdata.userplaylistinfo.createdat;                          //user specific loading song list.                         pfquery *querylikedislike = [pfquery querywithclassname:[songlikedislike parseclassname]];                         [querylikedislike wherekey:@"songid" equalto:songlistdata.songinfo.objectid];                         [querylikedislike wherekey:@"userid" equalto:[singleton getuserid]];                         [querylikedislike wherekey:@"playlistid" equalto:songlistdata.playlistinfo.objectid];                          [querylikedislike findobjectsinbackgroundwithblock:^(nsarray *objectslike, nserror *error) {                              gettotalobjectscount += 1;                              if(error == nil) {                                  if(objectslike.count) {                                      bool isdelete = [objectslike.lastobject[@"deleterecord"] boolvalue];                                     bool islike = [objectslike.lastobject[@"like"] boolvalue];                                      if(isdelete)                                         songlistdata.ratingtype = rating_gray;                                     else if(islike)                                         songlistdata.ratingtype = rating_green;                                     else                                         songlistdata.ratingtype = rating_red;                                 }                                  else                                     songlistdata.ratingtype = rating_gray;                             }                              else                                 nslog(@"problem while getting rating type");                              [arrparsesonglist addobject:songlistdata];                              nslog(@"i : %ld, objects : %ld",(long)gettotalobjectscount, (long)objects.count);                             if(gettotalobjectscount == objects.count)                                 [weakself processaftergettinglikesanddislikeinfo:arrparsesonglist];                         }];                     }                 });             }         }];     }];      nslog(@"in method -> operation : %ld",(long)self.opearation.operations.count); }  else     [uialertview showerrorwithmessage:no_internet handler:nil]; }  - (void)processaftergettinglikesanddislikeinfo:(nsmutablearray *)arrparsesonglist {  nspredicate *filtergrayout = [nspredicate predicatewithformat:@"isplaying == yes"]; nsarray *arrgrayout = [arrparsesonglist filteredarrayusingpredicate:filtergrayout];  nssortdescriptor *asortdescriptorgrayedout = [[nssortdescriptor alloc] initwithkey:@"alreadyplayedorder.intvalue" ascending:yes]; nsarray *arrgrayedoutsong = [nsmutablearray arraywitharray:[arrgrayout sortedarrayusingdescriptors:[nsarray arraywithobject:asortdescriptorgrayedout]]];  nspredicate *filternonplay = [nspredicate predicatewithformat:@"isplaying == no"]; nsarray *arrnonplay = [arrparsesonglist filteredarrayusingpredicate:filternonplay];  nssortdescriptor *asortdescriptorrating = [[nssortdescriptor alloc] initwithkey:@"totrating.intvalue" ascending:no]; nssortdescriptor *asortdescriptorcreateddate = [[nssortdescriptor alloc] initwithkey:@"createddate" ascending:yes];  nsarray *arrsortonnormalsong = [nsmutablearray arraywitharray:[arrnonplay sortedarrayusingdescriptors:[nsarray arraywithobjects:asortdescriptorrating,asortdescriptorcreateddate,nil]]];  if(self.arrsongsdata.count)     [self.arrsongsdata removeallobjects];  [self.arrsongsdata addobjectsfromarray:arrgrayedoutsong]; [self.arrsongsdata addobjectsfromarray:arrsortonnormalsong];  [self showhideloading:no]; [self.tblview reloaddata]; } 

and call in viewwilldisappear.

- (void)viewwilldisappear:(bool)animated {     [super viewwilldisappear:animated];      if(self.queryinstance)        [self.queryinstance cancel]; } 

thanks help!

so there number of things potentially keeping instance in memory:

1. you're adding operations operation queue, , operations retaining contents operations still in queue keep controller instance alive
2. your completion blocks using self rather creating __weak reference , using that, while blocks retained controller instance
3. in completion of first query you're starting query each of the, potentially 1000, results. not flood network requests, each 1 retaining controller instance
4. you potentially have 1000 queries running aren't cancelled, depending on when try cancel

mainly, should using weak references in completion blocks when try deallocate controller disappears , completions of queries silently run nothing in background. want cancel or prevent 1000 queries running if user isn't interested though...