ios - SDWebImageDownloader 返回零值

Question

SDWebImageDownloader 返回 nil 而不是 SDWebImageOperation 对象。下面的一些代码。

class PictureProvider: UIActivityItemProvider {
    private var originalLoadingOperation: SDWebImageOperation?

    fileprivate func loadOriginalImage(with link: String) {

        let imageDownloader = SDWebImageDownloader.shared()
        originalLoadingOperation = imageDownloader!.downloadImage(with: URL(string: link),
                                                               options: .continueInBackground,
                                                              progress: nil,
                                                             completed: { (image, data, error, finished) in 

                                                                 if image != nil
                                                                 {
                                                                     SDImageCache.shared().store(image, forKey: link)
                                                                 }
        })
    }
}

originalLoadingOperation 始终为“零”。