ios - Animate the changing of data in a collectionView -

i'd animate change in uicollectionview. have collectionview @iboutlet:

@iboutlet weak var collectionview: uicollectionview! 

and collection view reloads (so can change alpha of each cell) this:

var bulkawardmode = false;  @ibaction func bulkawardtoggleclicked(sender: uibutton) {     if(bulkawardmode == false) {         bulkawardmode = true     } else {         bulkawardmode = false     }     dispatch_async(dispatch_get_main_queue(), {         self.collectionview.reloaddata()     }) } 

however not animated, tried changing reloaddata() line self.collectionview.reloadsections(nsindexset(index: 0)), causes crash error attempt create view animation nil view.

i'm doing wrong, i'm not quite sure what. did try putting code in uiview.animatewithduration block, failed.

you can try:

collectionview.performbatchupdates({ () -> void in    // here can insert ,delete , animate cells }) { (success) -> void in        //completion block }