Why scale to fill give bigger image than UIImageVIew size? (using swift)

I'm trying to showing a list of place name, including it's photo using PFQueryTableViewController. It's included in ParseUI SDK from parse.com

I have managed to show the image. Unfortunately, when I change the UIImageView mode to Aspect fill, the image is become bigger than it should be.

here are the pictures:

https://dl.dropboxusercontent.com/u/86529526/pic_normal.png https://dl.dropboxusercontent.com/u/86529526/pic_error.png

in pic_normal, you will see two cell, with two normal image. in pic_error, you will the second cell was being overlaid by the first cell image.

can anyone help me to solve this problem? I also put my whole code here :

import UIKit

class TableViewController: PFQueryTableViewController, UISearchBarDelegate {

    @IBOutlet var searchBar: UISearchBar!


    // Initialise the PFQueryTable tableview
    override init(style: UITableViewStyle, className: String!) {
        super.init(style: style, className: className)
    }

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        // Configure the PFQueryTableView
        self.pullToRefreshEnabled = true
        self.paginationEnabled = false
    }

    // Define the query that will provide the data for the table view
    override func queryForTable() -> PFQuery {

        // Start the query object
        var query = PFQuery(className: "Places")

        // query with pointer
        query.includeKey("mainPhoto")

        // Add a where clause if there is a search criteria
        if searchBar.text != "" {
            query.whereKey("name", containsString: searchBar.text)
        }

        // Order the results
        query.orderByAscending("name")

        // Return the qwuery object
        return query
    }


    //override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: PFObject) -> PFTableViewCell? {
        var cell = tableView.dequeueReusableCellWithIdentifier("CustomCell") as! CustomTableViewCell!
        if cell == nil {
            cell = CustomTableViewCell(style: UITableViewCellStyle.Default, reuseIdentifier: "CustomCell")
        }

        // Extract values from the PFObject to display in the table cell
        if let name = object["name"] as? String{
            cell.name.text = name
        }

        // display initial image
        var initialThumbnail = UIImage(named: "question")
        cell.photo.image = initialThumbnail


        // extract image from pointer
        if let pointer = object["mainPhoto"] as? PFObject {
            cell.detail.text = pointer["photoTitle"] as? String!
            if let thumbnail = pointer["photo"] as? PFFile {
                cell.photo.file = thumbnail
                cell.photo.loadInBackground()
            }
        }
        cell.sendSubviewToBack(cell.photo)

        // return the cell
        return cell
    }




    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

        // Get the new view controller using [segue destinationViewController].
        var detailScene = segue.destinationViewController as! DetailViewController

        // Pass the selected object to the destination view controller.
        if let indexPath = self.tableView.indexPathForSelectedRow() {
            let row = Int(indexPath.row)
            detailScene.currentObject = objects[row] as? PFObject
        }
    }

    override func viewDidLoad(){
        super.viewDidLoad()
        let tapGesture = UITapGestureRecognizer(target:self, action:Selector("hideKeyboard"))
        tapGesture.cancelsTouchesInView = true
        tableView.addGestureRecognizer(tapGesture)
    }

    func hideKeyboard(){
        tableView.endEditing(true)
    }

    override func viewDidAppear(animated: Bool) {

        // Refresh the table to ensure any data changes are displayed
        tableView.reloadData()

        // Delegate the search bar to this table view class
        searchBar.delegate = self
    }

    func searchBarTextDidEndEditing(searchBar: UISearchBar) {

        // Dismiss the keyboard
        searchBar.resignFirstResponder()

        // Force reload of table data
        self.loadObjects()
    }

    func searchBarSearchButtonClicked(searchBar: UISearchBar) {

        // Dismiss the keyboard
        searchBar.resignFirstResponder()

        // Force reload of table data
        self.loadObjects()
    }

    func searchBarCancelButtonClicked(searchBar: UISearchBar) {

        // Clear any search criteria
        searchBar.text = ""

        // Dismiss the keyboard
        searchBar.resignFirstResponder()

        // Force reload of table data
        self.loadObjects()
    }

}

With content mode set to Aspect Fill, try setting clips to bounds to true as well, reason being the content mode aspect fill keeps on filling the frame of the image view till the frame is fully filled with content also keeping the aspect ratio intact. In the process of filling the container with image maintaining aspect ratio, either vertical or horizontal frame is fully filled, and the filling is continued till the other (if horizontal than vertical or vise versa) portion is fully filled. Thus the first filled portion either across vertical or horizontal will go out of bounds and the content will be visible outside the frame of the image view. To clip the extra content we need to clip the extra portion using imageView's clipsToBounds property set to true

cell.photo.contentMode = UIViewContentMode.ScaleAspectFill
cell.photo.clipsToBounds = true