objective c - Get friends' work data from facebook SDK on iOS -

i trying fetch work info fb friends on ios using facebook sdk. here's code using:

if (fbsession.activesession.isopen) {     nsmutabledictionary * params = [nsmutabledictionary dictionarywithobjectsandkeys:                                     @"work", @"fields",                                     nil];      fbrequest *request = [fbrequest requestwithgraphpath:@"me/friends" parameters:params httpmethod:@"get"];     [request startwithcompletionhandler:      ^(fbrequestconnection *connection, nsdictionary *result, nserror *error) {          if (!error) {              if (result) {                  if (result.count) {                      nsmutablearray *friendswithjobtitles = [nsmutablearray array];                      (id afriend in [result objectforkey:@"data"]) {                          if ([afriend objectforkey:@"work"]) {                              [friendswithjobtitles addobject:afriend];                          }                        }                      nslog(@"result = %@", friendswithjobtitles);                  }              }            }      }]; } 

the friendswithjobtitles blank reason. please help.