app/models/topic.rb
class Topic < ApplicationRecord
acts_as_paranoid column: :hidden_at
include ActsAsParanoidAliases
include Notifiable
belongs_to :community
belongs_to :author, -> { with_hidden }, class_name: "User", inverse_of: :topics
has_many :comments, as: :commentable, inverse_of: :commentable
validates :title, presence: true
validates :description, presence: true
validates :author, presence: true
scope :sort_by_newest, -> { order(created_at: :desc) }
scope :sort_by_oldest, -> { order(created_at: :asc) }
scope :sort_by_most_commented, -> { reorder(comments_count: :desc) }
end