Pagination for UICollectionView
<p>I have created datatable view using UICollectionView.</p>

<p>This is the code:</p>

<pre><code>class PanelViewController: UIViewController{

var TableHeaderArray = NSMutableArray()
var TableDataArray = NSMutableArray()
var NumberOfRows = Int()   
var UlockDataArray = NSMutableArray()
let dataSource = DataSource()

override func viewDidLoad() {
    super.viewDidLoad()

    dataSource.populateData()

    let noOfRows = dataSource.NumberOfRows
    self.NumberOfRows = noOfRows + 1

    self.UlockDataArray = dataSource.DUDataArray
    self.TableDataArray = dataSource.DTableDataArray   


    let layout: CustomCollectionViewLayout = CustomCollectionViewLayout()

    DataTableCollectionView = UICollectionView(frame: CGRect(x:0, y:0, width:self.TableVu.bounds.width, height:self.TableVu.bounds.height), collectionViewLayout: layout)
    DataTableCollectionView.dataSource = self
    DataTableCollectionView.delegate = self
    self.DataTableCollectionView .registerNib(UINib(nibName: "FixedCellIdentifier", bundle: nil), 
        forCellWithReuseIdentifier: FixedCellIdentifier)
    self.DataTableCollectionView .registerNib(UINib(nibName: "DynamoCellIdentifier", bundle: nil),
     forCellWithReuseIdentifier: DynamoCellIdentifier)

    self.TableVu.addSubview(DataTableCollectionView)        
    self.view.addSubview(TableVu)

}
</code></pre>

<p>}</p>

<pre><code>extension PanelViewController : UICollectionViewDataSource, UICollectionViewDelegate{
    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -&gt; Int{        
        return self.NumberOfRows
    }

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -&gt; Int {     
    return dataSource.TableHeaders.count        
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -&gt; UICollectionViewCell {

    // My Code to Create Cells using data from TableHeaderArray, TableDataArray and UlockDataArray

}


func scrollViewDidScroll(scrollView: UIScrollView) {
    let offsetY = scrollView.contentOffset.y
   let contentHeight = scrollView.contentSize.height
   var returnUmidData = NSMutableArray()
   var returnTableData = NSMutableArray()

   if offsetY &gt; contentHeight - scrollView.frame.size.height {   

        self.dataSource.populateData()

        returnUData = self.dataSource.DUDataArray
        returnTableData = self.dataSource.DTableDataArray


        let seconds = 5.0
        let delay = seconds * Double(NSEC_PER_SEC)
        let dispatchTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))

        dispatch_after(dispatchTime, dispatch_get_main_queue(), {

             self.NumberOfRows += returnTableData.count

             let mergetWorkoutData = NSMutableArray(array: self.UlockDataArray)
             mergetWorkoutData.addObjectsFromArray(returnUmidData as [AnyObject])

             self.UlockDataArray = mergetWorkoutData

             let mergetWorkoutTabelData = NSMutableArray(array: self.TableDataArray)
             mergetWorkoutTabelData.addObjectsFromArray(returnTableData as [AnyObject])

             self.TableDataArray = mergetWorkoutTabelData 

            self.DataTableCollectionView!.reloadData()

        })
   }
}
</code></pre>

<p>}</p>

<p>Initialy, I am displaying first 50 records. I need to implement pagination on vertical scroll.
Each time user reach to end of scroll, I want to make an API call to get the next 50 records.</p>

<p>But in doing so, I am getting an error</p>

<pre><code>"Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]:
 index 51 beyond bounds [0 .. 50]'"
</code></pre>

<p>I think somehow indexPath is not getting updated but unable to understand where and why or how to update it. Can you please advise?</p>