didSelectItemAt and didDeSelectItemAt from UICollectionView

Question

If I use didSelectItemAt in a UICollectionView, I want to change the color of the selected cell. And with didDeselectItemAt, I want to replace the color of the previously selected cell.

It works well before moving. However, moving to the far right will not work properly. Why is this?

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

        return 14 
 }

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CalendarCollectionViewCell", for: indexPath ) as! CalendarCollectionViewCell

        cell.calendarDayLabel.text = calendar?.twoWeeksDay![ indexPath.row ]
        cell.calendarDateLabel.text = calendar?.twoWeeksDate![ indexPath.row ]

        return cell

 }

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        let cell = collectionView.cellForItem(at: indexPath) as? CalendarCollectionViewCell


        cell?.calendarDayLabel.textColor = UIColor( red: 255, green: 0, blue: 0, alpha: 1.0 )
        cell?.calendarDateLabel.textColor = UIColor( red: 255 , green: 255 , blue: 255 , alpha: 1.0 )
        cell?.calendarCircleImageView.isHidden = false

        self.selectYear = self.calendar?.twoWeeksYear![ indexPath.row ]
        self.selectMonth = self.calendar?.twoWeeksMonth![ indexPath.row ]
        self.selectDate = self.calendar?.twoWeeksDate![ indexPath.row ]
        self.selectDay = self.calendar?.twoWeeksDay![ indexPath.row ]

        self.selectDateTime.text = self.selectYear! + "년 " + self.selectMonth! + "월 " + self.selectDate! + "일 " + self.selectDay!

        self.selectDateTime.isHidden = false

}

    func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {


        let cell = collectionView.cellForItem(at: indexPath) as? CalendarCollectionViewCell
        cell?.calendarDayLabel.textColor = UIColor( red: 0, green: 0, blue: 0, alpha: 1.0 )
        cell?.calendarDateLabel.textColor = UIColor( red: 0 , green: 0 , blue: 0 , alpha: 1.0 )
        cell?.calendarCircleImageView.isHidden = true

 }

enter image description here

Answer 1

Because cells are reused

 var selectedIndex:IndexPath?

//

 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CalendarCollectionViewCell", for: indexPath ) as! CalendarCollectionViewCell

       if indexPath == selectedIndex {

                cell.calendarDayLabel.textColor = UIColor( red: 255, green: 0, blue: 0, alpha: 1.0 )
                cell.calendarDateLabel.textColor = UIColor( red: 255 , green: 255 , blue: 255 , alpha: 1.0 )
                cell.calendarCircleImageView.isHidden = false

       }
       else {

              cell.calendarDayLabel.textColor = UIColor( red: 0, green: 0, blue: 0, alpha: 1.0 )
              cell.calendarDateLabel.textColor = UIColor( red: 0 , green: 0 , blue: 0 , alpha: 1.0 )
              cell.calendarCircleImageView.isHidden = true

       }


}

 func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    selectedIndex = indexPath
    collectionView.reloadData()

 }

Remove didDeselectItemAt