relation inheritance

gistfile1.rb

class PostQuery

  attr_accessor :relation

  ALLOWED_SORT_ATTRS = ["title", "updated_at"]

  # @example PostQuery.new.relation.recent.sorted("title", "DESC")
  # @example PostQuery.new(user.posts).relation.recent.sorted("title", "DESC")
  #
  def initialize(relation = nil)
    relation ||= Post.all
    self.relation = relation.extending(Scopes)
  end

  module Scopes
    include BaseQuery::Scopes

    def recent
      where("updated_at > ?", 1.day.ago)
    end
  end

end

class BaseQuery

  module Scopes
    def sorted(sort_param, sort_direction)
      # This won't work
      # How to access this const in included module
      if ALLOWED_SORT_ATTRS.include(sort_param)
        order("#{sort_param} #{sort_direction}")
      else
        order("id DESC")
      end
    end
  end

end

This doesn't work either and actually removes the const from the sub class:

class PostQuery < BaseQuery

  attr_accessor :relation

  ALLOWED_SORT_ATTRS = ["title", "updated_at"]

  # @example PostQuery.new.relation.recent.sorted("title", "DESC")
  # @example PostQuery.new(user.posts).relation.recent.sorted("title", "DESC")
  #
  def initialize(relation = nil)
    super(relation ||= Post.all)
    @relation = @relation.extending(Scopes)
  end

  module Scopes
    def recent
      where("updated_at > ?", 1.day.ago)
    end
  end

end

class BaseQuery

  def initialize(relation)
    @relation = relation.extending(Scopes)
  end

  def self.inherited(sub_klass)
   # uninitialized constant PostQuery:: ALLOWED_SORT_ATTRS
    puts sub_klass.const_get(: ALLOWED_SORT_ATTRS)
  end

  module Scopes
    def sorted(sort_param, sort_direction)
      # This won't work
      # How to access this const in included module
      if ALLOWED_SORT_ATTRS.include(sort_param)
        order("#{sort_param} #{sort_direction}")
      else
        order("id DESC")
      end
    end
  end

end