@@ -1,7 +1,5 @@
 class Exercise < ActiveRecord::Base
-  has_many :classifications, as: :classifiable, dependent: :destroy
   has_many :statuses, as: :completeable, dependent: :destroy
-  has_many :topics, through: :classifications
   has_one :trail, through: :step, as: :completeables
   has_one :step, dependent: :destroy, as: :completeable
 
class Exercise < ActiveRecord::Base
  has_many :classifications, as: :classifiable, dependent: :destroy
  has_many :statuses, as: :completeable, dependent: :destroy
  has_many :topics, through: :classifications
  has_one :trail, through: :step, as: :completeables
  has_one :step, dependent: :destroy, as: :completeable

  validates :name, presence: true
  validates :url, presence: true

  def self.ordered
    order(:created_at)
  end

  def self.public
    where(public: true)
  end
end

Should we have a migration to delete classification data for exercises? Is there any?