Retrofit 2 send file

gistfile1.txt

    private fun buildMultipartBody(filePaths: List<Uri>): MultipartBody.Builder {
        val builder = MultipartBody.Builder().setType(MultipartBody.FORM)

        filePaths.forEachIndexed { i, uri ->
            val extension = "jpeg"
            val mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension)

            crashlyticsLog(uri, extension, mimeType)

            val file = getFileFromUri(uri)

            builder.addFormDataPart(
                    "image_files[$i]",
                    "filename$i.$extension",
                    RequestBodyBuffer(MediaType.parse(mimeType), file)
            )
        }
        return builder
    }

    override fun networkExecute(repository: Repository): Single<Response<Report>> {
        return repository.sendReport(buildMultipartBody(imagesPaths).build())
    }
    
    // Repository
    
    override fun sendReport(build: MultipartBody): Single<Response<Report>> {
        return restApi.postReport(build)
    }
    
    // Rest Api interface
    
    @POST(REPORT)
    fun postReport(@Body build: MultipartBody): Single<Response<Report>>