通过关联created_at，或者通过自己的created_at如果没有关联订单 [英] Order by association created_at, or by own created_at if no association

问题描述

我的模型组的has_many的帖子，帖子have_many评论。

My group model has_many posts, posts have_many comments.

当我告诉一组帖子，我想在最近的评论中创建的，如果有任何一个职位，或职位本身的created_at订购。

When I show the posts on a group, I want to order by the created at of the most recent comment, if there are any on a post, or by the created_at of the post itself.

所以，旧的文章会跳回到列表的顶部，如果它有一个新的注释。

So an old post would jump back to the top of the list if it has a new comment.

推荐答案

我会坚持一点点不同的方法：你的评论belongs_to的：POST 和 belongs_to的接受：触摸选项。将其设置为真正和你的帖子的的updated_at 将自动更新的注释的修改。这样你就可以自由地展示自己的帖子被下令的updated_at 。

I would stick to a little different approach: your Comment belongs_to :post and belongs_to accepts :touch option. Set it to true and your Post's updated_at will be automatically updated on a Comment's modification. This way you can freely show your posts ordered by their updated_at.

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