oldhaven/app/models/music/track.rb

class Track < ActiveRecord::Base
  belongs_to :album
  has_many :track_artists
  has_many :artists, :through => :track_artists
  has_many :playlist_items
  
  after_save :clear_artist_cache
  
  def duration
    if self.length
      time = self.length
      time_m = (time / 60).floor
      time_s = time - time_m * 60
      time_m.to_s + ':' + (time_s < 10 ? '0' : '') + time_s.to_s
    else
      '0:00'
    end
  end
  
  def serialize
    {
      id: id,
      artist: artists.first.name,
      album: album.name,
      position: position.to_s(36),
      name: name,
      length: length,
      duration: duration,
      available: available,
      album_pic: album.pic_url
    }
  end
  
private

  def clear_artist_cache
    artists.each(&:clear_cache)
  end
end