How to sort by created_at column of association in rails?

Question

Here are my associations:

Class Post
belongs_to :user
has_many :favorites, :dependent => :destroy
has_many :favoriters, :through => :favorites, :source => :user
end

Class User
has_many :posts
has_many :favorites,  :dependent => :destroy
has_many :favorited, :through => :favorites, :source => :post
end

Class Favorites
belongs_to :user, :post
end

I want to sort users' favorite posts by the created_at column of the Favorites association. However, this sorts by the Post created_at attribute, not the Favorites created_at attribute. How can I sort by the Favorites created_at attribute?

 @[email protected]('created_at DESC')

Answer 1

You need to specify which table you want to use in the order by clause.

@posts = @user.favorited.order('posts.created_at DESC')

ought to do it.

One nice trick is to use the rails console when inspecting associations. Specifically, it helps to use the 'to_sql' method on Active Record queries you are performing.

For instance:

% bundle exec rails console

> u = User.last
> u.favorited.order('created_at DESC').to_sql

Answer 2

use this in your post model for set default order:

default_scope { order("created_at DESC") }