Rails的3排序相关的型号 [英] Rails 3. sort by associated model

问题描述

让我们说我有两个型号：课程和ScheduledCourse

Let's say I have two models: Course and ScheduledCourse.

该课程模式有一个name属性。

The Course model has a name attribute.

当然的has_many：预定课程 scheduled_courses：belongs_to的课程

course has_many :scheduled courses scheduled_courses :belongs_to course

courses
id | name
 1 | biology
 2 | history
 3 | chemistry
 4 | literature

scheduled_courses
id | course_id 
 1 | 2
 2 | 4
 3 | 1
 4 | 2

我怎样才能让一个ActiveRecord查询到预定的课程按字母顺序排序？

How can I make an ActiveRecord query to sort the scheduled courses alphabetically?

推荐答案

试试...

ScheduledCourse.joins(:course).order('course.name')

如果这不起作用，你可能需要调用。所有之前，你的加入条件，像这样：

If this doesn't work, you may need to call .all before your joins condition, like so:

ScheduledCourse.all.joins(:course).order('course.name')

喜欢的 luacassus 的说，<一个href="http://stackoverflow.com/questions/1530131/rails-order-using-a-has-many-belongs-to-relationship">this的回答可以帮助;我认为这个问题的答案语法是pre-阿雷尔（ActiveRecord的3），但它会完成这项工作。希望帮助！

Like luacassus said, this answer can help; I think the syntax in that answer is pre-Arel (ActiveRecord 3), but it'll get the job done. Hope that helps!

编辑：

正如刚才@FellowStranger，正确的语法时下似乎

As mentioned by @FellowStranger, the correct syntax nowadays seems to be

ScheduledCourse.joins(:course).order('courses.name')

这篇关于Rails的3排序相关的型号的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！