Haml：如果条件在 Haml 中为真，则追加类 - Haml: Append class if condition is true in Haml

问题：

If post.published?如果post.published?

.post
  / Post stuff

Otherwise除此以外

.post.gray
  / Post stuff

I've implemented this with rails helper and it seems ugly.我已经用 rails helper 实现了这个，它看起来很难看。

= content_tag :div, :class => "post" + (" gray" unless post.published?).to_s do
  / Post stuff

Second variant:第二个变体：

= content_tag :div, :class => "post" + (post.published? ? "" : " gray") do
  / Post stuff

Is there a more simple and haml-specific way?有没有更简单和特定于haml的方法？

UPD.更新。 Haml-specific, but still not simple:特定于 Haml，但仍然不简单：

%div{:class => "post" + (" gray" unless post.published?).to_s}
  / Post stuff

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解决方案：

参考一： https://en.stackoom.com/question/EUQa
参考二： https://stackoom.com/question/EUQa