Multiple calls to a Alamofire request, get reference for each call

Question

I have used Alamofire for uploading images in multipart form data. I am successful in achieving my target. Each time I upload an image, I call the "uploadDocWebService" function. So the number of times the function is called, is equal to the number of images. I am hopeless in identifying the result of each call. My images are uploaded successfully. In case there is a server failure, or internet connection failure the uploading fails, I cannot identify which image I should delete from the view, that has failed. I pass indexPath as a parameter for each image upload. But that indexPath updates to the latest image upload before I receive the result for the first image upload. Can any one suggest me a better approach for this situation.

Here is the code I use for image upload:

func uploadDocWebservice(fileUrl: NSURL , progressView : PWProgressView , index : String , imageData : NSData? , name : String , mimeType : String , uploadType : String){

    let url = "\(kBaseURL)\(uploadDocsUrl)"

    var type = String()
    var networkGroupId = String(SingletonClass.sharedInstance.selectedNetworkId!)

    if SingletonClass.sharedInstance.groupPopUp == true {

        type = "group"
        networkGroupId = String(SingletonClass.sharedInstance.selectedSubNetworkOrGroup!)

    }else {

        type = "network"
    }

    Alamofire.upload(
        .POST,
        url,
        multipartFormData: { multipartFormData in

            if uploadType == "Image" {
                multipartFormData.appendBodyPart( data: imageData! , name: "file", fileName: name, mimeType: mimeType)
            }else {
                multipartFormData.appendBodyPart(fileURL: fileUrl, name: "file")
            }
            multipartFormData.appendBodyPart(data:"\(SingletonClass.sharedInstance.tokenId)".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!, name :"token")
            multipartFormData.appendBodyPart(data:"\(type)".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!, name :"networkGroup")
            multipartFormData.appendBodyPart(data:"\(networkGroupId)".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!, name :"networkGroupId")

        },
        encodingCompletion: { encodingResult in
            switch encodingResult {
            case .Success(let upload, _, _):

                upload.progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in

                    let ratio: Float = Float(totalBytesRead) / Float(totalBytesExpectedToRead)
                    // Call main thread.
                    dispatch_async(dispatch_get_main_queue(), {
                        progressView.progress = ratio
                    })

                }

                upload.responseJSON { response in

                    let dataString = NSString(data: response.data!, encoding:NSUTF8StringEncoding)
                    print(dataString)

                    self.edited = true

                    do{

                        let json = try NSJSONSerialization.JSONObjectWithData(response.data!, options: .MutableLeaves) as? NSDictionary

                        if let success = json!["success"] as? Int {

                            if success == 1 {

                                let id = json!["response"]!.objectForKey("id") as! String
                                let docName = "\(json!["response"]!.objectForKey("name") as! String).\(json!["response"]!.objectForKey("ext") as! String)"
                                let dic = ["name" : docName , "Id" : id]
                                self.uploadedDocsIdArray.addObject(dic)
                                self.uploadedArrayJustNames.addObject(docName)
                                print(self.uploadedDocsIdArray)

                            }else {

                                // delete image from view here

                            }

                        }

                    }catch{

                        // delete image from view here
                        invokeAlertMethod("Error", msgBody: "Invalid Json", delegate: self)

                    }

                }
            case .Failure(let encodingError):

                print(encodingError)
            }
        }
    )

}

If I get to know the which result is associated to which call, that could help me delete that particular image from view.

You need to have unique id for each image OR something which is uniquely associated with each image. For example, you can have a separate upload tracking dictionary containing image-Ids as keys and its value as a Bool. Initially all values will be "false". Whenever upload is successful for an image-Id you can set that value to "true". — san, Feb 02 '16 at 06:21
I have already tried this. In case there is a connection or server failure I will not be returned the image id that is failed. Failed images can be more than one. — Amrit Sidhu, Feb 02 '16 at 06:38
Then, you can set that value against that image-id to true and remove the image(from view) associated with that id. I think I am not able to understand your problem completely. Sorry. — san, Feb 02 '16 at 07:10
I donot want to remove the image in case of success. The image needs to be removed only in case of failure. — Amrit Sidhu, Feb 02 '16 at 07:20
You can check for the inverted set then - let's say you know you have image ids [123, 456, 789], you know 123 and 789 are successful, so the one missing is 456 and thus must be deleted. — Drmorgan, Mar 29 '16 at 18:23
@Drmorgan : I tried this case also. But is there any hope we can get a reference to the call. For example : If I call the request for the first time, the request should be tagged as first request. All requests should be tagged . Is there any such solution?? — Amrit Sidhu, Mar 30 '16 at 04:01
@AmritSidhu you mentioned previously that you get the image-id for successful uploads. If that is still true you don't need to tag the requests - as soon as you receive the success you will know which ones succeeded. Then once all requests are complete you can check to see which are missing from the set/array of successful image downloads. To check when multiple requests are complete, I would checkout `dispatch_group` to be notified when a group of tasks are complete. RayWenderlich has a great example of dispatch groups https://www.raywenderlich.com/63338/grand-central-dispatch-in-depth-part-2 — Drmorgan, Mar 30 '16 at 14:40
I will that a simple `completionHandler` closure would do the trick. The caller always has enough context and you can persist the context in the completion handler. — Sulthan, Apr 02 '16 at 11:39

Nagra · Accepted Answer · 2016-04-02T11:41:22.040

You need to keep a reference to the original request, should be the same for upload requests I think. Try the following:

func uploadDocWebservice(fileUrl: NSURL , progressView : PWProgressView , index : String , imageData : NSData? , name : String , mimeType : String , uploadType : String) -> Request? {
    return Alamofire.upload ...
}

Then you can simply have an array of requests i.e: var requests: [Request](). When calling Alamofire.upload / Alamofire .request - it returns a Request object.

You can then do:

var requests: [Request]()
let request = uploadDocWebservice(...)
requests.append(request)

Then you can just loop through the array and check whatever request you wish.

Multiple calls to a Alamofire request, get reference for each call

1 Answers1