repositories_banana.rb

module Repositories
  class Banana
    attr_reader :relation

    def initialize(relation = ::Banana.all)
      self.relation = relation
    end

    def old
      self.class.new(
        relation.where("created_at < ?", 3.weeks.ago)
      )
    end

    def sweet
      self.class.new(
        relation.where(sweet: true)
      )
    end

    private

    attr_writer :relation
  end
end

# bananas_controller.rb
@bananas = Repositories::Banana.new.old.sweet