GroupItem：Class的未定义方法“属性”

Question

我是Ruby的新手，我正在尝试使新功能正常工作。我写了以下课程：

class ::GroupItem
  attributes :group_enabled,
             :list_count

  def group_enabled
    true
  end

  def include_group_enabled?
    Topic.group_enabled object
  end

  def list_count
    object.list_count
  end

  def include_list_count?
    include_group_enabled?
  end
end

我运行bundle exec puma，由于某种原因，出现以下错误：

! Unable to load application: NoMethodError: undefined method `attributes' for GroupItem:Class
Did you mean?  attr_writer
bundler: failed to load command: puma (/home/user/.rbenv/versions/2.6.2/bin/puma)
NoMethodError: undefined method `attributes' for GroupItem:Class
Did you mean?  attr_writer

奇怪的是，当我将第一行替换为：

 ::GroupItem.class_eval do # instead of class ::GroupItem

有效。问题是什么？我该怎么解决？