通过Swift 3.0生成并导出GIF动画？

Question

我已经了解到，根据文档，自从iOS 9以来，Image IO Framework已经在语法上发生了变化，但是我已经完成了我的研究，并且以下代码似乎是正确的。我必须遵守下列程序;一个过程拍摄图像并将这些图像作为gif写入应用程序的文档文件夹。我可以确认这是有效的，因为如果我使用iTunes转到应用程序的文档文件夹，我可以查看实际的gif文件。尽管如此，在我尝试从同一个文件中读取的第二个过程中，抛出一个错误，指出该路径上的文件不存在。我已经发布了以下代码。

class GifManager {
private func getDocumentsDirectory() -> URL?  {
    return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
}

public func generateGif(photos: [UIImage], filename: String) -> Bool {
    if let docsDirectory = getDocumentsDirectory() {
        let url = docsDirectory.appendingPathComponent(filename)
        let fileProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: 0]]
        let gifProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFDelayTime as String: 0.125]]
        if let destination = CGImageDestinationCreateWithURL(url as CFURL, kUTTypeGIF, photos.count, nil) {
            CGImageDestinationSetProperties(destination, fileProperties as CFDictionary?)
            for photo in photos {
                CGImageDestinationAddImage(destination, photo.cgImage!, gifProperties as CFDictionary?)
            }
            return CGImageDestinationFinalize(destination)
        }
    }
    return false
}

public func saveGifToCameraRoll(filename: String) {
    if let docsDirectory = getDocumentsDirectory() {
        let fileUrl: URL = docsDirectory.appendingPathComponent(filename)
        do {
            let data = try Data(contentsOf: fileUrl)
            if let _ = UIImage(data: data) {
                PHPhotoLibrary.shared().performChanges({
                    PHAssetChangeRequest.creationRequestForAssetFromImage(atFileURL: fileUrl)
                    }, completionHandler: {completed, error in
                        if error != nil {
                            print("error")
                        } else if completed {
                            print("completed")
                        } else {
                            print("not completed")
                        }
                })
            }

        } catch let error {
            print(error)
        }
    }
}