Dynamic cell size based on screenWidth

CollectionCellSize.swift

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let totalAvailableWidth = collectionView.bounds.width
        let padding: CGFloat = 25
        let interSpace: CGFloat = 15
        let numOfCellInaRow: CGFloat = 3
        let cellWidth: CGFloat = (totalAvailableWidth - (padding * 2) - (interSpace * (numOfCellInaRow - 1))) / numOfCellInaRow
        /// padding * 2 = leading + trailing space, (interSpace * (numOfCellInaRow - 1)) = totalInterspacing as 3 cells will have 2 interspace
        let cellSize = CGSize(width: cellWidth, height: cellWidth)
        return cellSize
}