ios - NSPredicate keeps crashing my app -

i've created searchbar thats suppose filter uitableview have setup. i'm using parse.com pull array down app.

- (void)viewdidload {      [super viewdidload];      // additional setup after loading view.       [self query];       //[self.searchdisplaycontroller.searchresultstableview registernib:[uinib nibwithnibname:@"searchcell" bundle:nil] forcellreuseidentifier:@"searchdata"];  } - (void)didreceivememorywarning {      [super didreceivememorywarning];      // dispose of resources can recreated. } -(void)query {      pfquery *q = [pfquery querywithclassname:@"_user"];       [q selectkeys:@[@"username"]];       [q findobjectsinbackgroundwithblock:^(nsarray *objects, nserror *error) {          if (!error) {               nslog(@"load array);               searharray = [[nsarray alloc] initwitharray:objects];              }          else{               nslog(@"array no good");          }        }]; } 

then attempt filter array using these lines of code

-(void)searchbar:(uisearchbar *)searchbar textdidchange:(nsstring *)searchtext {      self.searchterm = searchtext; }  -(void)searchbarcancelbuttonclicked:(uisearchbar *)searchbar {      [self.mysearchbar resignfirstresponder];      //reset original array , reload table      self.filteredcities = searharray;      [self.mytableview reloaddata]; }  -(void)searchbarsearchbuttonclicked:(uisearchbar *)searchbar {      [self.mysearchbar resignfirstresponder];       if ([self.searchterm isequaltostring:@""]) {          // nothing here - reset original array , reload table          self.filteredcities = searharray;      } else {          // filter array based on term searched using predicate          nspredicate *predicate = [nspredicate predicatewithformat:@"self.title contains[c] %@",self.searchterm];          self.filteredcities = [nsarray arraywitharray:[searharray filteredarrayusingpredicate:predicate]];      }      [self.mytableview reloaddata]; }   -(void)searchbartextdidbeginediting:(uisearchbar *)searchbar {      self.filteredcities = searharray;      [self.mytableview reloaddata]; }   

but keeps crashing. i've debugged problem down line

self.filteredcities = [nsarray arraywitharray:[searharray filteredarrayusingpredicate:predicate]]; 

the error is:

`2015-03-31 19:31:19.783 pondu[59307:5149459] *** terminating app due uncaught exception 'nsinternalinconsistencyexception', reason: 'key "words" has no data.  call fetchifneeded before getting value.' *** first throw call stack: (0x18724a59c 0x1979a00e4 0x18724a4dc 0x1000c34bc 0x1880350f0 0x18807b934 0x18807b394 0x18807a084 0x188079e58 0x1000b31b0 0x18be207ac 0x18ba30d34 0x18ba19e48 0x18bbf91dc 0x18bbc3f04 0x18bd80890 0x18bd80540 0x18ba24950 0x18811ddf0 0x1872029ec 0x187201c90 0x1871ffd40 0x18712d0a4 0x1902cf5a4 0x18ba623c0 0x1000b1f64 0x19800ea08) libc++abi.dylib: terminating uncaught exception of type nsexception` 

self.searchterm seems nsstring put there supposing value nsdictionary. need use

@"self matches %@"

, not

@"self.title matches %@"