如何在alamofire中同步上传图片？

Question

Im using swift 3 and Alamofire 4 . I want to upload 6 images inside a for loop but alamofire upload request run asynchronously. What it does is it runs for loop first and then the upload. But i want to wait until i get a response and then upload next. How can i do this?

Answer 1

You should use a serial DispatchQueue to run your image uploads sequentially. The serial queue will ensure that only one request will be run at a time and the next one only starts when the previous one finished execution.

let serialQueue = DispatchQueue(label: "serialQueue")
for image in images {
    serialQueue.async{
       //upload image with Alamofire here
    }
}

Answer 2

Model Class

class MultipartUpdataData: NSObject
{
    var mediaData:Data!
    var mediaUploadKey:String!
    var fileName:String!
    var mimeType:String!
    override init()
    {

    }
    required   init(coder aDecoder: NSCoder) {

        if let mediaData = aDecoder.decodeObject(forKey: "mediaData") as? Data {

            self.mediaData = mediaData
        }
        if let mediaUploadKey = aDecoder.decodeObject(forKey: "mediaUploadKey") as? String {

            self.mediaUploadKey = mediaUploadKey
        }
        if let fileName = aDecoder.decodeObject(forKey: "fileName") as? String {

            self.fileName = fileName
        }
        if let mimeType = aDecoder.decodeObject(forKey: "mimeType") as? String {

            self.mimeType = mimeType
        }
    }
    open func encodeWithCoder(_ aCoder: NSCoder)
    {
        if let mediaData = self.mediaData{
            aCoder.encode(mediaData, forKey: "mediaData")
        }
        if let mediaUploadKey = self.mediaUploadKey {
            aCoder.encode(mediaUploadKey, forKey: "mediaUploadKey")
        }
        if let mimeType = self.mimeType {
            aCoder.encode(mimeType, forKey: "mimeType")
        }
        if let fileName = self.fileName {
            aCoder.encode(fileName, forKey: "fileName")
        }
    }

}

Upload Image, First make sure to append imageData into array then call this function like below:-

 var uploadMediaList  = [MultipartUpdataData]()
for loop{
let multiObject  = MultipartUpdataData()
            multiObject.mediaData = self.pngImageData!
            multiObject.mimeType = "image/png"
            multiObject.mediaUploadKey = "profile_pic" //Replace this key with your existing key.
            let profileFilename = self.filename(Prefix: "profile", fileExtension: "png")
            multiObject.fileName = profileFilename
            uploadMediaList.append(multiObject)
}
self.upload(uploadMediaList)

func upload(multipartImages:[MultipartUpdataData]){
        let parameters:[String:String] = ["key":"value"]
        Alamofire.upload(
            multipartFormData: { multipartFormData in


                for mData in multipartImages!{
                    let pngImageData = mData.mediaData
                    let uploadfileNamekey = mData.mediaUploadKey
                    let fileName = mData.fileName!
                    let mimeType = mData.mimeType!
                    multipartFormData.append(pngImageData!, withName: uploadfileNamekey!, fileName: fileName, mimeType: mimeType)

                }
                for (key, value) in parameters {
                    multipartFormData.append(value.data(using: String.Encoding(rawValue: String.Encoding.utf8.rawValue), allowLossyConversion: true)!, withName: key)
                }

        },
            to: "\(url)",
            encodingCompletion: { encodingResult in
                switch encodingResult {
                case .success(let upload, _, _):
                    upload.responseJSON { response in
                        let json = JSON(data: response.data!)

                    print("SUCSESS")

                    }
                case .failure(let encodingError):
                   print("ERORR")

                }
        }
        )
    }
//MARK:-filename-
    func filename(Prefix:String , fileExtension:String)-> String
    {
        let dateformatter=DateFormatter()
        dateformatter.dateFormat="MddyyHHmmss"
        let dateInStringFormated=dateformatter.string(from: NSDate() as Date )
        return  NSString(format: "%@_%@.%@", Prefix,dateInStringFormated,fileExtension) as String
    }

Answer 3

You can use DispatchGroup class.

DispatchGroup allows for aggregate synchronization of work.

You can use them to submit multiple different work items and track when they all complete, even though they might run on different queues.

This behavior can be helpful when progress can't be made until all of the specified tasks are complete.

Sample code:

let dispatchGroup = DispatchGroup()

var i = 0
for element in yourImageArray {
    dispatchGroup.enter()
    i = i+1

    Alamofire.request("https://httpbin.org/get", parameters: ["foo": "bar"]).responseJSON { response in
        print("Finished request \(i)")
        dispatchGroup.leave()
    }
}

dispatchGroup.notify(queue: .main) {
    print("Finished all requests.")
}