crystal attribute declaration problem

downloader.cr

require "yaml"
require "logger"

class WebcamDownloader::Downloader
  def initialize
    @logger = Logger.new(STDOUT)

    @webcam_array = WebcamArray.new
  end

  def setup
    @webcam_array.logger = @logger
    @webcam_array.setup
  end
end

webcam_array.cr

class WebcamDownloader::WebcamArray
  property :logger

  def initialize
  end

  def setup
    logger.debug "#{self.class} setup"
  end
end