Manage multiple add-ons with ReactiveX (on iOS with Swift and Alamofire)

Question

I try to upload several photos to the server using ReactiveX (RxSwift), collect responses from each request and then make one final request to complete the submission.

Everything seems to work quite well until I try to complete reduceall the answers. The final one is subscribeNextnever called. (Perhaps I do not understand how they work flatMapor reduce?)

In particular, this is how I try to perform this procedure.

• Prepare the observable to encode each photo ( self.imageMgris an instance PHCachingImageManager())

  func getPhotoDataObservable(asset: PHAsset) -> Observable<NSData> {
      return create { observer in
          self.imageMgr.requestImageForAsset(asset,
              targetSize: PHImageManagerMaximumSize,
              contentMode: .AspectFit,
              options: nil,
              resultHandler: { (myImage, myInfo) -> Void in
                  let data = UIImageJPEGRepresentation(myImage!, 1.0)!
                  NSLog("Encoded photo")
                  observer.onNext(data)
                  self.converts += 1
                  if self.converts == self.userReview.photos.count {
                      NSLog("Completed encoding photos")
                      observer.onCompleted()
                  }
              })
          return NopDisposable.instance
      }
  }
  

• Prepare each photo you want to upload after encoding (using Alamofire and RxAlamofire)

  func getPostPhotoObservable(photoData: NSData) -> Observable<ReviewPhotoObject> {
      return create { observer in
          NSLog("Uploading Photo")
  
          upload(.POST,
              urlRequest.URLString,
              headers: nil,
              multipartFormData: { mfd in
                  mfd.appendBodyPart(data: photoData, name: "image", fileName: "image", mimeType: "image/jpeg")
              },
              encodingMemoryThreshold: Manager.MultipartFormDataEncodingMemoryThreshold,
              encodingCompletion: { encodingResult in
                  switch encodingResult {
                  case .Success(let upload, _, _):
                      upload.responseJSON(completionHandler: { (myResponse) -> Void in
                          if let photoResponse = myResponse.result.value {
                              let photoObject = photoResponse.objectForKey("photo")!
                              let photo = ReviewPhotoObject()
                              photo.photoID = photoObject.objectForKey("id")! as! NSNumber
                              NSLog("Uploaded Photo")
                              observer.onNext(photo)
                          }
  
                          self.uploads += 1
                          if self.uploads == self.userReview.photos.count {
                              NSLog("Completed uploading photos")
                              observer.onCompleted()
                          }
                      })
  
                  case .Failure(let encodingError):
                      observer.onError(encodingError)
                      print(encodingError)
                  }
              })
  
          return NopDisposable.instance
      }
  }
  

• Finally all together

  func postReview(review: MyReview) {
      self.userReview = review
  
      _ = review.photos.toObservable().flatMap { photos in
          return self.getPhotoDataObservable(photos)
      }.flatMap { photoData in 
          return self.getPostPhotoObservable(photoData)
      }.reduce([], { var accumulator, photo: ReviewPhotoObject) -> [Int] in
          accumulator.append(Int(photo.photoID))
          return accumulator
      }).subscribeNext({ (photoIds) -> Void in
          print(photoIds) // Never called
      })
  }
  

(, ) :

Encoded photo
Uploading photo
Encoded photo
Uploading photo
Completed encoding photos
Uploaded photo
Uploaded photo
Completed uploading photos

subscribeNext . RxSwift - , , - , .

Answer 1

, , , , . PHAsset, , . , , , reduce , , .

( Swift 3 2.)

extension PHImageManager {

    func requestMaximumSizeImage(for asset: PHAsset) -> Observable<UIImage> {
        return .create { observer in
            let request = self.requestImage(for: asset, targetSize: PHImageManagerMaximumSize, contentMode: .aspectFit, options: nil, resultHandler: { image, info in
                if let image = image {
                    observer.onNext(image)
                    observer.onCompleted()
                }
                else if let info = info, let error = info[PHImageErrorKey] as? Error {
                    observer.onError(error)
                }
            })
            return Disposables.create { self.cancelImageRequest(request) }
        }
    }
}

, PHImageManager , . , , , , . , JPEG. JPEG :

    let imagesData = review.photos.toObservable().flatMap {
        self.imageMgr.requestMaximumSizeImage(for: $0)
    }.map {
        UIImageJPEGRepresentation($0, 1.0)
    }.filter { $0 != nil }.map { $0! }

, JPEG, , . imagesData - Observable<Data>.

getPostPhotoObservable , , , . , Observable , ReviewPhotoObject.

:

• , , , ReviewPhotoObject , ( , . ) , concat flatMap.

• - , . , -, - . catchErrorJustReturn, catchError .