records_controller.rb

# app/controllers/records_controller.rb

def some_method
  ... business logic ...

  attaching_images = params[:record][:images].presence
  if attaching_images
    attaching_images = attaching_images.map do |im|
      tempfile = ImageConverter.new(tempfile: im.tempfile, width: 1200).call
      ActionDispatch::Http::UploadedFile.new(
        {
          filename: "#{im.original_filename.split('.').first}.jpg",
          tempfile: tempfile,
          type: 'image/jpg',
          head: "Content-Disposition: form-data; name=\"property[images][]\"; filename=\"#{im.original_filename.split('.').first}.jpg\"\r\nContent-Type: image/jpg\r\n"
        }
      )
    end
  end
  
  if record.new(permitted_params.merge(images: attaching_images)).save
    ...
  else
    ...
  end
end