ios - UICollectionView. How to insert new items behind the scene? -

i have collectionview 1 row. in performance purposes on start load part of items , scroll (let be) 6th item of 30. insert rest of items (it can hundred) in beginning , collection view switches new 6 element not stays on old. i've tried use scrolltoitematindexpath on insertion completion, shows new item first , switching old.

how insert new items behind scene? mean force collectionview behave in way if no updates made , items were?

- (void)adddatestorage { nsdate* currentpastdate = [datestorage objectatindex:0];  nsmutablearray* indexpathes = [nsmutablearray array];  for(int i=0; i<days_in_year; i++) {     [datestorage insertobject:currentpastdate atindex:0];      currentpastdate = [currentpastdate datebyaddingtimeinterval:seconds_in_day*(-1)];      [indexpathes addobject:[nsindexpath indexpathforrow:i insection:0]];   }      [self.calendar insertitemsatindexpaths:indexpathes];  } 

i've tried use performbatchupdates: , reloaddata, have same result.

first, need modify model (load more elements).

second, tell collectionview reload data (it should see updated number of elements , still show visible elements) , no scrolling needed.