         if var firstCell = visibleCell.first {
             var leftEdge = firstCell.frame.minX
             while leftEdge > minX {
-                leftEdge = placeNewCellOnLeft(with: leftEdge, index: firstCell.index!, dataSource: dataSource)
+                leftEdge = placeNewCellOnLeft(with: leftEdge, index: firstCell.index, dataSource: dataSource)
                 firstCell = visibleCell.first!
             }
         }


open class PagingMenuCell: UIView {
    var identifier: String!
    var index: Int?
}

public protocol PagingMenuViewDataSource: class {

    
    private func align() {
        visibleCell.forEach { (cell) in
            let leftEdge = (0..<cell.index).reduce(CGFloat(0)) { (sum, idx) in sum + frameQueue[idx].width }
            cell.frame.origin.x = leftEdge
        }
    }
