mysql - Rails 3 ActiveRecord: Order by count on association

Question

I have a model named Song. I also have a model named Listen. A Listen belongs_to :song, and a song :has_many listens (can be listen to many times).

In my model I want to define a method self.top which should return the top 5 songs listened to the most. How can I achieve that using the has_many relation?

I'm using Rails 3.1.

Thanks!

Answer 1

Using named scopes:

class Song
  has_many :listens
  scope :top5,
    select("songs.id, OTHER_ATTRS_YOU_NEED, count(listens.id) AS listens_count").
    joins(:listens).
    group("songs.id").
    order("listens_count DESC").
    limit(5)

Song.top5 # top 5 most listened songs