如何在Ruby on Rails中通过关联订购has_many? [英] How do I order a has_many through association in Ruby on Rails?

问题描述

考虑到以下AR模型，当给定任务的句柄时，我想按姓氏字母对用户进行排序:

Given the following AR models, I would like to sort users alphabetically by last name when given a handle to a task:

#user
has_many :assignments
has_many :tasks, :through => :assignments    

#assignment
belongs_to :task
belongs_to :user

#task
has_many :assignments
has_many :users, :through => :assignments

我想获得一个任务，然后导航到其分配的用户，并按字母顺序对用户列表进行排序.

I would like to get a task then navigation to its assigned users, and sort the user list alphabetically.

我一直认为我应该能够像这样将:order子句添加到has_many :users, :through => :assignments:

I keep thinking that I should be able to add the :order clause to has_many :users, :through => :assignments like this:

#task.rb
has_many :assignments
has_many :users, :through => :assignments, :order => 'last_name, first_name'

但是这不起作用.

给定任务后，如何按last_name对用户进行排序?

How can I sort users by last_name when given a task?

推荐答案

由于Rails 4中不推荐使用条件参数，因此应使用范围块:

Since condition arguments are deprecated in Rails 4, one should use scope blocks:

has_many :users, -> { order 'users.last_name, users.first_name' }, :through => :assignments

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