RxSwift with AWSS3

Upload creation observable

return create { (observer: AnyObserver<UploadSignal>) -> Disposable in
            
            let transferUtility = AWSS3TransferUtility.defaultS3TransferUtility()
            let key = String(format: "uploads/%@.png", arguments: [NSUUID().UUIDString])
            let fullUrl = String(format: "https://s3.amazonaws.com/edenmessenger/%@", arguments: [key])
            
            
            var uploadTask : AWSS3TransferUtilityUploadTask?
            var completionUploadTask : AWSS3TransferUtilityUploadTask?
            
            transferUtility?.uploadData(data, bucket: Constants.awsS3BucketName, key: key, contentType: "image/png", expression: nil, completionHander: { (uploadTask, err) -> Void in
                completionUploadTask = uploadTask
                if let error = err {
                    observer.onError(error)
                }else {
                    observer.onNext(UploadSignal(uploadedUrl: fullUrl, uploadProgress: 1))
                    observer.onCompleted()
                }
            }).continueWithBlock({ (task) -> AnyObject! in
                if let error = task.error {
                    observer.onError(error)
                }
                
                if let exception = task.exception {
                    print("AWS Upload Exception :", exception.description)
                }
                
                if let thisUploadTask = task.result as? AWSS3TransferUtilityUploadTask {
                    uploadTask = thisUploadTask
                }
                return task
            })
            
            return AnonymousDisposable{ [weak uploadTask, completionUploadTask] in
                uploadTask?.cancel()
                completionUploadTask?.cancel()
            }
        }