 
 open class PagingMenuCell: UIView {
     var identifier: String!
-    var index: Int?
+    var index: Int!
+    var isSelected: Bool = false
 }
 
 public protocol PagingMenuViewDataSource: class {

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

    
    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
        }
    }
