This gist includes a Rails helper and controller code that lets you sort on custom columns alongside the meta-search gem search and sort features

meta_search_custom_column_sort.rb

# Helper method - place in application_helper.rb

  def custom_sort_helper(path, sort_term, sort_label, search, sort_string)
    uri = String.new(path)
    
    # copy the current search terms but exclude meta_sort
    search_array = Array.new  
    search.search_attributes.each { |key, val| (search_array << "search[#{key}]=#{val}") unless key == 'meta_sort'  }
	  
    uri << '?'
    if search_array.length > 0
      uri << search_array.join('&') << '&'
    end
    
    if sort_string =~ /#{sort_term}\.desc$/
      uri << "custom_sort=#{sort_term}.asc"
      sort_label << '&nbsp;&#9660;'
    elsif sort_string =~ /#{sort_term}\.asc$/
      uri << "custom_sort=#{sort_term}.desc"
      sort_label << '&nbsp;&#9650;'
    else
      uri << "custom_sort=#{sort_term}.asc"
    end
    link_to(raw(sort_label), uri)
  end

# Example code for your controller index action
# In this example for a Companies controller, a company can have many Antibodies via a has_many_through association
# The code allows sorting on Company columns and on the Number of Antibodies associated with a company

  def index
    @search = Company.search(params[:search])
    @custom_sort = nil

    if params[:custom_sort] and params[:custom_sort] =~ /^n_antibodies/
      if params[:custom_sort] =~ /desc$/
          @companies = @search.all.uniq.sort_by{ |a| -a.antibodies.length }.paginate :page => params[:page], :per_page => 20
          @custom_sort = 'n_antibodies.desc'
      else
          @companies = @search.all.uniq.sort_by{ |a| a.antibodies.length }.paginate :page => params[:page], :per_page => 20
          @custom_sort = 'n_antibodies.asc'
      end
    else
      @search.meta_sort ||= 'name.asc'
      @companies = @search.all.paginate :page => params[:page], :per_page => 20
    end
  end


# Here is the code that goes into the Index view for the column that contains the Number of Antibodies

    <%= custom_sort_helper(companies_path, 'n_antibodies', '# Antibodies', @search, @custom_sort) %>