 import ObjectiveC
 
 private var downloadTaskKey: UInt8 = 0
+
 public extension UIImageView {
     var downloadTaskIdentifier: String? {
         get {

        Vincent.sharedInstance.invalidate(self.downloadTaskIdentifier)
        self.downloadTaskIdentifier = nil
    }
}
        }
        
        if let url = url {
            self.downloadTaskIdentifier = Vincent.sharedInstance.downloadImageFromUrl(url, cacheType: cacheType, success: {[weak self] image in
                self?.downloadTaskIdentifier = nil
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self?.image = image
                    completion?(error: nil, image: image)
                })
                }, error: {[weak self] (error: NSError) -> () in
