iphone - Can't understand why my tableview with GCD is crashing -

i've finished re-writing this, , covered every conceivable angle can think of. don't know why crashing. perhaps me figure out.

this cellforrowatindexpath code:

- (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {     static nsstring *cellidentifier = @"cell";     jhomeviewcell *cell = (jhomeviewcell *)[tableview dequeuereusablecellwithidentifier:cellidentifier];     if (cell == nil) {         cell = [[jhomeviewcell alloc] initwithstyle:uitableviewcellstyledefault                                     reuseidentifier:cellidentifier];         cell.delegate = self;     }      cell.cellcontent.cellinfo = [self cellinfoforcellatindexpath:indexpath];     if (cell.cellcontent.cellinfo.thumbnailscomplete == yes || cell.cellcontent.cellinfo.thumbnailsbeingcreated == yes) {         [cell.cellcontent setneedsdisplay];     }     else {         [cell.cellcontent setup];     }       return cell; } 

and in cellcontent, there's setup method:

-(void)setup {      [self setneedsdisplay];      self.cellinfo.thumbnailsbeingcreated = yes;      nsmanagedobjectid *entryid = self.cellinfo.objectid;      dispatch_queue_t cellsetupqueue = dispatch_queue_create("com.journalized.setupcell", null);     dispatch_async(cellsetupqueue, ^{         nsmanagedobjectcontext *newmoc = [[nsmanagedobjectcontext alloc] init];          nspersistentstorecoordinator *coordinator = [[coredatastore mainstore] context].persistentstorecoordinator;          [newmoc setpersistentstorecoordinator:coordinator];         nsnotificationcenter *notify = [nsnotificationcenter defaultcenter];         [notify addobserver:self                     selector:@selector(mergechanges:)                         name:nsmanagedobjectcontextdidsavenotification                       object:newmoc];          entry *entry = (entry *)[newmoc objectwithid:entryid];          [newmoc save:nil];         int = 0;          while (i < self.cellinfo.numberofthumbnailstodraw) {         nslog(@"number of thumbnails: %i %i %i", self.cellinfo.numberofthumbnailstodraw, entry.media.count, i);             media *media = [entry.media objectatindex:i];             uiimage *image = [media getthumbnail];              bool success = [newmoc save:nil];              //nslog(@"time: %@ success: %i", entry.entrytableinfo.creationtimestring, success);              [self.cellinfo.thumbnails setobject:image forkey:[nsnumber numberwithint:i]];             i++;         }         [[nsnotificationcenter defaultcenter] removeobserver:self];          dispatch_async(dispatch_get_main_queue(), ^{              self.cellinfo.thumbnailscomplete = yes;              [self setneedsdisplay];         });      });     dispatch_release(cellsetupqueue); 

it crashes on line:

media *media = [entry.media objectatindex:i]; 

with error:

index 1 beyond bounds [0 .. 0] 

the nslog above that...

nslog(@"number of thumbnails: %i %i %i", self.cellinfo.numberofthumbnailstodraw, entry.media.count, i); 

gives result:

number of thumbnails: 2 1 1 

which sort of explains crash, except value set in [cellinfoforcellatindexpath:]; method, so:

cellinfo.numberofmediaitems = entry.media.count; cellinfo.numberofthumbnailstodraw = min(cellinfo.numberofmediaitems, 3); 

i don't know problem occurring, or why it's occurring, can't move on app until part fixed.

well numberofthumbnailstodraw 2 meaning while loop 0, 1, count of entry.media 1 has 0 index of course it'll crash.