ios - didDeselectItemAt indexPath doesn't triggered when another cell is selected -

i'm trying implement feature: in app, if selected cell in uicollectionview, borders becomes blue, , if select one, previous should deselected , borders should become transparent. there methods i've written:

func collectionview(_ collectionview: uicollectionview, cellforitemat indexpath: indexpath) -> uicollectionviewcell {         let cell = collectionview.dequeuereusablecell(withreuseidentifier: reuseidentifier, for: indexpath) as! chatcell          /* set settings */         if globalselected[indexpath.item] {             cell.circleview.layer.bordercolor = uicolor.blue.cgcolor         } else {             cell.circleview.layer.bordercolor = uicolor.clear.cgcolor         }          return cell }  func collectionview(_ collectionview: uicollectionview, didselectitemat indexpath: indexpath) {     //global variable maintain selection     global.selectedchatpath = indexpath     globalselected[indexpath.item] = true     collectionview.reloaddata() }  func collectionview(_ collectionview: uicollectionview, diddeselectitemat indexpath: indexpath) {     if indexpath != nilpath {         globalselected[indexpath.item] = false         collectionview.reloaddata()     } } 

the nilpath indexpath(item: -1, section: 0), doesn't matter, because collectionview(_ collectionview: uicollectionview, diddeselectitemat indexpath: indexpath) isn't called. collectionview has allowselection = true , allowsmultipleselection = false properties. thankful help.

if single cell supposed selected @ same time recommend put selected index path instance variable (nil means nothing selected)

var selectedindexpath : indexpath? 

in cellforitematset colors depending on instance variable

func collectionview(_ collectionview: uicollectionview, cellforitemat indexpath: indexpath) -> uicollectionviewcell {     let cell = collectionview.dequeuereusablecell(withreuseidentifier: reuseidentifier, for: indexpath) as! chatcell      /* set settings */     if let selected = selectedindexpath, selected == indexpath {         cell.circleview.layer.bordercolor = uicolor.blue.cgcolor     } else {         cell.circleview.layer.bordercolor = uicolor.clear.cgcolor     }      return cell } 

in didselectitemat reload previous , new selected cells , set selectedindexpath new selected index path. more efficient reloading entire collection view.

func collectionview(_ collectionview: uicollectionview, didselectitemat indexpath: indexpath) {     //global variable maintain selection      var cellstoreload = [indexpath]     if let selected = selectedindexpath {         cellstoreload.append(selected)     }     selectedindexpath = indexpath     collectionview.reloaditems(at: cellstoreload) } 

diddeselectitemat needed if want deselect cell explicitly.