iphone - Why is my core data not updating? -

i update core data in background thread, so:

entry.message = [self contentfornotewithedml:note.content]; entry.datalastmodified = [nsdate date]; [entry.managedobjectcontext save:nil];  dispatch_async(dispatch_get_main_queue(), ^{     nserror *error;      if (![[self fetchedresultscontroller] performfetch:&error]) {         nslog(@"unresolved error %@, %@", error, [error userinfo]);     }      [self.tableview reloaddata]; }); 

on each cell of tableview, displays different entry fetchedresultscontroller. on main thread, nslog in cellforrowatindexpath on datalastmodified date, , date doesn't change recent value. if close app , run again, updates contents of cell , datalastmodified date changes correct value.

it seems changing data, required, tableview isn't seeing changes until app restarted. ideas why?

edit: doing nslog in cellforrowatindexpath on background thread gives the correct data, doing on main thread not.

edit 2: how background context works:

nsnotificationcenter *notificationcenter = [nsnotificationcenter defaultcenter];  [notificationcenter     addobserver:[appdelegate applicationdelegate].coredatamanager     selector:@selector(mergechanges:)     name:nsmanagedobjectcontextdidsavenotification     object:[appdelegate applicationdelegate].coredatamanager.managedobjectcontext]; nspersistentstorecoordinator *journaldatapsc = [appdelegate applicationdelegate].coredatamanager.managedobjectcontext.persistentstorecoordinator;  dispatch_queue_t addorupdateentriesqueue = dispatch_queue_create("com.app.addorupdateentries", null); dispatch_async(addorupdateentriesqueue, ^{      nsmanagedobjectcontext *journaldatamoc = [[nsmanagedobjectcontext alloc] init];     [journaldatamoc setpersistentstorecoordinator:journaldatapsc];      //some code me entry on context     entry.message = [self contentfornotewithedml:note.content];     entry.datalastmodified = [nsdate date];     [entry.managedobjectcontext save:nil];      [[nsnotificationcenter defaultcenter] removeobserver:[appdelegate applicationdelegate].coredatamanager];     dispatch_async(dispatch_get_main_queue(), ^{         nserror *error;          if (![[self fetchedresultscontroller] performfetch:&error]) {             nslog(@"unresolved error %@, %@", error, [error userinfo]);         }          [self.tableview reloaddata];     }); }); dispatch_release(addorupdateentriesqueue); 

make sure you're using moc's correctly, not thread-safe , can used in thread created in. in case, if you're doing right enter.managedobjectcontext different moc of fetched results controller (which in main thread).

that means saves in background not propagated main thread moc. make sure handle nsmanagedobjectcontextdidsavenotification in main thread adding observer when create fetched results controller.

looking @ code here few points notice:

• you should register save notification thrown background moc not main thread moc.
• you should initialize background moc initwithconcurrencytype: using nsprivatequeueconcurrencytype
• once you're using nsprivatequeueconcurrencytype it's better use performblock: make changes , save instead of using low-level gcd dispatch methods.