Query actions in Rails contollers

application_controller.rb

class ApplicationController < ActionController

  def wiki
    @wiki ||= if (current_user.admin?)
                AdminWiki.new
              else
                ReadonlyWiki.new
              end
  end

end

cards_controller.rb

class CardsController < ApplicationController

  def recently_changed
    render 'recently_changed', locals: {
      cards: RecentlyChanged.new(wiki).cards,
    }
  end

end

statistics_controller.rb

class StatisticsController < ApplicationController

  def traffic
    hits_by_date = statistics.page_hits_by_date
    render 'traffic', locals: {
      weekly_page_hits: statistics.weekly_page_hits(hits_by_date),
      weekday_hits:     statistics.hits_by_weekday(hits_by_date),
      time_of_day_hits: statistics.hits_by_time_of_day,
    }
  end

end