从iOS将多个图像上传到S3的有效方法

我在应用程序中将Amazon S3用作文件存储系统。我所有的item对象都有几个与之关联的图像，并且每个对象仅存储图像URL，以保持数据库的轻量化。因此，我需要一种有效的方法直接从iOS将多个图像上传到S3，并在成功完成后将它们的URL存储在我发送给服务器的对象中。我仔细研究了Amazon提供的SDK和示例应用程序，但是我遇到的唯一示例是单个图像上传，操作如下：

 func uploadData(data: NSData) {
    let expression = AWSS3TransferUtilityUploadExpression()
    expression.progressBlock = progressBlock

    let transferUtility = AWSS3TransferUtility.defaultS3TransferUtility()

    transferUtility.uploadData(
        data,
        bucket: S3BucketName,
        key: S3UploadKeyName,
        contentType: "text/plain",
        expression: expression,
        completionHander: completionHandler).continueWithBlock { (task) -> AnyObject! in
            if let error = task.error {
                NSLog("Error: %@",error.localizedDescription);
                self.statusLabel.text = "Failed"
            }
            if let exception = task.exception {
                NSLog("Exception: %@",exception.description);
                self.statusLabel.text = "Failed"
            }
            if let _ = task.result {
                self.statusLabel.text = "Generating Upload File"
                NSLog("Upload Starting!")
                // Do something with uploadTask.
            }

            return nil;
    }
}

对于5张以上的图片，这将成为一团糟，因为我必须等待每次上传成功返回后才能启动下一个，然后最终将对象发送到我的数据库。我是否需要有效，干净的代码来实现自己的目标？

亚马逊示例应用程序github的URL：https : //github.com/awslabs/aws-sdk-ios-samples/tree/master/S3TransferUtility-Sample/Swift

这是我用来同时将多个图像上传到S3的代码DispatchGroup()。

func uploadOfferImagesToS3() {
    let group = DispatchGroup()

    for (index, image) in arrOfImages.enumerated() {
        group.enter()

        Utils.saveImageToTemporaryDirectory(image: image, completionHandler: { (url, imgScalled) in
            if let urlImagePath = url,
                let uploadRequest = AWSS3TransferManagerUploadRequest() {
                uploadRequest.body          = urlImagePath
                uploadRequest.key           = ProcessInfo.processInfo.globallyUniqueString + "." + "png"
                uploadRequest.bucket        = Constants.AWS_S3.Image
                uploadRequest.contentType   = "image/" + "png"
                uploadRequest.uploadProgress = {(bytesSent:Int64, totalBytesSent:Int64, totalBytesExpectedToSend:Int64) in
                    let uploadProgress = Float(Double(totalBytesSent)/Double(totalBytesExpectedToSend))

                    print("uploading image \(index) of \(arrOfImages.count) = \(uploadProgress)")

                    //self.delegate?.amazonManager_uploadWithProgress(fProgress: uploadProgress)
                }

                self.uploadImageStatus      = .inProgress

                AWSS3TransferManager.default()
                    .upload(uploadRequest)
                    .continueWith(executor: AWSExecutor.immediate(), block: { (task) -> Any? in

                        group.leave()

                        if let error = task.error {
                            print("\n\n=======================================")
                            print("? Upload image failed with error: (\(error.localizedDescription))")
                            print("=======================================\n\n")

                            self.uploadImageStatus = .failed
                            self.delegate?.amazonManager_uploadWithFail()

                            return nil
                        }

                        //=>    Task completed successfully
                        let imgS3URL = Constants.AWS_S3.BucketPath + Constants.AWS_S3.Image + "/" + uploadRequest.key!
                        print("imgS3url = \(imgS3URL)")
                        NewOfferManager.shared.arrUrlsImagesNewOffer.append(imgS3URL)

                        self.uploadImageStatus = .completed
                        self.delegate?.amazonManager_uploadWithSuccess(strS3ObjUrl: imgS3URL, imgSelected: imgScalled)

                        return nil
                    })
            }
            else {
                print(" Unable to save image to NSTemporaryDirectory")
            }
        })
    }

    group.notify(queue: DispatchQueue.global(qos: .background)) {
        print("All \(arrOfImages.count) network reqeusts completed")
    }
}

这是关键部分，我至少损失了5个小时。NSTemporaryDirectory 每个图片的 URL都必须不同！

class func saveImageToTemporaryDirectory(image: UIImage, completionHandler: @escaping (_ url: URL?, _ imgScalled: UIImage) -> Void) {
    let imgScalled              = ClaimitUtils.scaleImageDown(image)
    let data                    = UIImagePNGRepresentation(imgScalled)

    let randomPath = "offerImage" + String.random(ofLength: 5)

    let urlImgOfferDir = URL(fileURLWithPath: NSTemporaryDirectory().appending(randomPath))
    do {
        try data?.write(to: urlImgOfferDir)
        completionHandler(urlImgOfferDir, imgScalled)
    }
    catch (let error) {
        print(error)
        completionHandler(nil, imgScalled)
    }
}

希望这会有所帮助！