Lighter View Controller (UICollectionViewDatasource) in Swift

CollectionViewDataSource.swift

//
//  CollectionViewDataSource.swift
//
//  Created by Bill Richards on 10/1/14.
//  Copyright (c) 2014 Bill Richards. All rights reserved.
//

import Foundation

typealias CollectionViewCellConfigureBlock = (cell:UICollectionViewCell, item:AnyObject?) -> ()

class CollectionViewDataSource: NSObject, UICollectionViewDataSource {
    
    var items:NSArray = []
    var itemIdentifier:String?
    var configureCellBlock:CollectionViewCellConfigureBlock?
    
    init(items: NSArray, cellIdentifier: String, configureBlock: CollectionViewCellConfigureBlock) {
        self.items = items
        self.itemIdentifier = cellIdentifier
        self.configureCellBlock = configureBlock
        super.init()
    }
    
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return items.count
    }
    
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(self.itemIdentifier!, forIndexPath: indexPath) as UICollectionViewCell
        let item: AnyObject = self.itemAtIndexPath(indexPath)
        
        if (self.configureCellBlock != nil) {
            self.configureCellBlock!(cell: cell, item: item)
        }
        
        return cell
    }
    
    func itemAtIndexPath(indexPath: NSIndexPath) -> AnyObject {
        return self.items[indexPath.row]
    }
}

CustomUICollectionViewCell.swift

//
//  CustomUICollectionViewCell.swift
//
//  Created by Bill Richards on 9/24/14.
//  Copyright (c) 2014 Bill Richards. All rights reserved.
//

import UIKit

class CustomUICollectionViewCell: UICollectionViewCell {

    //Example cell configuration
    func configureForItem(item:AnyObject) {
        //do something with the cell...
    }
    
}

ViewController.swift

//
//  ViewController.swift
//
//  Created by Bill Richards on 10/7/14.
//  Copyright (c) 2014 Bill Richards. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    //variable to hold reference to the datasource
    var dataSource:CollectionViewDataSource?

    override func viewDidLoad() {
        super.viewDidLoad()
    
        //Init our datasource and setup the closure to handle our cell
        //modify 'AnyObject' to match your model
        self.dataSource = CollectionViewDataSource(items: self.items, cellIdentifier: "Cell", configureBlock: { (cell, item) -> () in
            if let actualCell = cell as? CustomUICollectionViewCell {
                if let actualItem = item as? AnyObject {
                    actualCell.configureForItem(actualItem)
                }
            }
        })
    
        //finally, set the collectionview datasource
        self.collectionView.dataSource = self.dataSource
    
    }
    
}

Why not use a generic class rather than NSArray instead?