dynamic-paths.rb

module AdminHelper

  def link_to_direction(field, title = nil)
    title ||= field.humanize
    dir = @order_dir.downcase == 'asc' ? 'desc' : 'asc'
    link_to title, yield(:order => field, :dir => dir) if block_given?
  end
end

= link_to_direction('name') {|params| admin_artists_path(params)}