import UIKit
import AssetsLibrary

class AlbumsTableViewController: UITableViewController {

    var albums:ALAssetsGroup[] = []

    func loadAlbums(){
        let library = IAAssetsLibraryDefaultInstance

        library.enumerateGroupsWithTypes(ALAssetsGroupType(ALAssetsGroupAll),usingBlock: {(group,stop) in
                if group {
                    self.albums.append(group)
                }
                else {
                    dispatch_async(dispatch_get_main_queue(),{

                        self.tableView.reloadData()

                    })
                }
            },failureBlock: { (error:NSError!) in println("Problem loading albums: \(error)") })

    }

    override func viewDidLoad() {
        super.viewDidLoad()
        loadAlbums()

        // Uncomment the following line to preserve selection between presentations
        // self.cleaRSSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        //self.navigationItem.rightBarButtonItem = self.editButtonItem
    }

但是else块不会执行。我得到的错误是：

'performSelectorOnMainThread' is unavailable: 'performSelector' methods are unavailable

那么swift中“performSelectorOnMainThread”的替代方法是什么？

更新：

我现在得到一个中止错误。这是控制台的样子：http://cl.ly/image/3D0h1x433P0R