 
     private func _toCache(URL: NSURL, image: UIImage?) {
         if let image = image {
-            delegate.cache[URL] = image
+            delegate?.cache[URL] = image
         }
     }
 


    private let decompressingQueue = dispatch_queue_create(nil, DISPATCH_QUEUE_CONCURRENT)

    init(configuration: NSURLSessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration(),
        cache: ImageCache = Diskcached()
        ) {
            session = NSURLSession(configuration: configuration, delegate: delegate, delegateQueue: nil)

*/
public class Loader {

    weak var delegate: Manager?
    let task: NSURLSessionDataTask
    var receivedData = NSMutableData()
    internal var blocks: [Block] = []
