Using Alamofire to upload multiple Images serially

Question

I am developing an app, and one the function is letting our user to submit comments for a product with photos. And when I developing the image upload part, I got stuck with the following issue:

If user selected more than 1 photos, How can I upload the images to sever through RESTful API serially. I don't want to let user upload image concurrently. If one of the photo upload failed, I don't want the following photo to continue uploading. That means, photo should upload one by one, and one of them failed, then uploading process will stop, and call the completion callback with false. If all uploaded, then call the completion with true.

So what should I do to accomplish this goal? Any suggestion?

I am using Xcode 7.3.1 + Swift 2 + Alamofire 3 to upload the images. My code goes here:

import UIKit
import Alamofire


class TestAlamofireMultiUpload: UIViewController {

    var apiUrl: String {
        get {
            return "http://192.168.6.183:8000/api/v1/"  // SD Lib
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let images = [UIImage(named: "test1")!, UIImage(named: "test2")!]
        requestAPIUploadImage("jo21ij3ndooi3okvdani3u43ijfdnk", images: images) { (result) in
            print(result)
        }
    }

    /// Upload file with multipart formdata
    func apiUploadFile(url: String,
                       method: Alamofire.Method,
                       token: String?,
                       multipartFormData: MultipartFormData -> Void,
                       completionHandler: (Response<AnyObject, NSError> -> Void)) {

        let headers = buildHeaders(token)

        Alamofire.upload(method,
                         "\(apiUrl)\(url)/",
                         headers: headers,
                         multipartFormData: multipartFormData,
                         encodingMemoryThreshold: Manager.MultipartFormDataEncodingMemoryThreshold,
                         encodingCompletion: {
                            (encodingResult) in
                            switch encodingResult {
                            case .Success(let request, _, _):
                                request
                                    .validate()
                                    .responseJSON(completionHandler: completionHandler)
                            case .Failure(let err):
                                let error = NSError(domain: "test", code: 1, userInfo: ["message": String(err)])
                                let result: Result<AnyObject, NSError> = .Failure(error)
                                let response = Response(request: nil, response: nil, data: nil, result: result)
                                completionHandler(response)
                            }
        })


    }

    /// Upload image
    func requestAPIUploadImage(token: String, images: [UIImage], completion: ((result: Bool) -> Void)) {

        let parameters = ["imageCategory": "1"]

        ////////////////////////////////////////////////////////////
        /// How can I make the images upload serially here ????? ///
        ////////////////////////////////////////////////////////////
        let image = images[0]

        self.apiUploadFile("image/upload", method: .POST, token: token, multipartFormData: {
            (multipartFormData) in

            // import images to multipart
            if let data = UIImageJPEGRepresentation(image, 1) {
                multipartFormData.appendBodyPart(data: data, name: "imageFile", fileName: "imageFile.jpeg", mimeType: "image/jpeg")
            }

            // import parameters to multipart
            for (key, value) in parameters {
                multipartFormData.appendBodyPart(data: value.dataUsingEncoding(NSUTF8StringEncoding)!, name: key)
            }

            }, completionHandler: {
                (response) in
                switch response.result {
                case .Success(let value):
                    print(value)
                    completion(result: true)
                case .Failure(let error):
                    print(error)
                    completion(result: false)
                }
        })
    }

    private func buildHeaders(token: String?) -> [String: String]? {
        var headers = [String: String]()
        if let token = token {
            headers["Authorization"] = "Token \(token)"
        }
        return headers
    }
}

Thanks in advance.