controller.rb

  def index
    @articles = Article.admin

    @for = params[:for]
    if @for.nil? || @for == "all"
      @for = "all"
    else
      for_method = "for_#{@for}"
      @articles = @articles.send(for_method.to_sym)
    end

    @order = params[:order]
    @articles = @articles.ordered_by_urgent
    if @order == "views"
      @articles = @articles.ordered_by_views_count
    elsif @order == "dated"
      @articles = @articles.ordered_by_created_at
    elsif @order == "datea"
      @articles = @articles.ordered_by_created_at_asc
    elsif @order == "placement"
      @articles = @articles.ordered_by_placement
    elsif @order == "category"
      @articles = @articles.ordered_by_category
    else
      @articles = @articles.ordered_by_title
    end

    @articles = @articles.ordered_by_id
    @articles = @articles.paginate :page => params[:page], :per_page => 50
  end

model.rb

  scope :ordered_by_title,
    order("LOWER(title) ASC")

  scope :ordered_by_views_count,
    order("views_count DESC")

  def self.for_tomorrow
    placement_day(1.day.from_now)
  end

  def self.for_today
    placement_day(0.day.from_now)
  end

  def self.placement_day date
    where(:placement_date => date.to_date)
  end