How do I automatically sort a has_many relationship in Rails?

Question

You can specify the sort order for the bare collection with an option on has_many itself:

class Article < ActiveRecord::Base 
  has_many :comments, :order => 'created_at DESC'
end 
class Comment < ActiveRecord::Base 
  belongs_to :article 
end

Or, if you want a simple, non-database method of sorting, use sort_by:

article.comments.sort_by &:created_at

Collecting this with the ActiveRecord-added methods of ordering:

article.comments.find(:all, :order => 'created_at DESC')
article.comments.all(:order => 'created_at DESC')

Your mileage may vary: the performance characteristics of the above solutions will change wildly depending on how you’re fetching data in the first place and which Ruby you’re using to run your app.

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