您如何通过在 SQL 中没有属性的自定义模型方法进行排序? [英] How do you order by a custom model method that has no attribute in SQL?

问题描述

以前我这样订购我的帖子:

Previously I ordered my posts as this:

@posts = Post.find(:all, :order => "created_at DESC")

但现在我想用我在 Post 模型中编写的自定义方法替换 created_at，该方法给出一个数字作为结果.

But now I want to replace created_at with a custom method I wrote in the Post model that gives a number as its result.

我的猜测:

@posts = Post.find(:all, :order => "custom_method DESC")

失败了..

推荐答案

它失败了，因为您要求您的数据库进行排序.

It fails because you are asking your db to do the sorting.

@posts = Post.all.sort {|a,b|a.custom_method <=>b.custom_method}

请注意，当您想要开始分页结果并且不再希望获取 .all 时，这变得非常重要.在开始之前先考虑一下您的设计.

Note that this becomes non-trivial when you want to start paging results and no longer wish to fetch .all. Think about your design a bit before you go with this.

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