Decode datatables ajax request URL in ruby controller

datatables_ajax_url_decode.rb

  # Process AJAX request generated by jquery datatables plugin, prepare an object which contains information to be used in 
  # ActiveRecord operation, result object properties tbd
  def decode_datatables_req
    cols_count = params['iColumns'].to_i
    row_start = params['iDisplayStart'].to_i
    rows_per_page = params['iDisplayLength'].to_i
    search_text = params['sSearch']
    sort_cols_count = params['iSortingCols'].to_i

    columns = (0..cols_count-1).map { |i| params["mDataProp_#{i}"] }
    # Suffix table name by grabbing from current control, to avoid ambigious col issue which might occured during ordering
    sort_columns = (0..sort_cols_count-1).map do |i|
      col_name = columns[params["iSortCol_#{i}"].to_i]
      col_name = "#{params[:controller]}.#{col_name}" unless col_name.index('.')
      { 
        :col => col_name, 
        :direction => params["sSortDir_#{i}"] 
      }
    end

    # Now let's rock it and do the processing
    {
      per_page: rows_per_page,
      page: row_start/rows_per_page + 1,
      columns: columns,
      cols_count: cols_count,
      sort_cols_count: sort_cols_count,
      sort_columns: sort_columns,
      sort_statement: (sort_columns.map {|col| "#{col[:col]} #{col[:direction]}"}).join(', '),
      search_text: search_text
    }

sample_usage.rb

  def get_rows
    dt = decode_datatables_req

    # Extra filtering for type and branch id
    where_array = []
    where_array << "branches.chinese_name like :keyword or branches.english_name like :keyword" unless params['keyword'].blank?

    search_obj = {
        :include => [],
        :order => dt[:sort_statement],
        :conditions => [where_array.join(' AND '), { :keyword => "%#{params['keyword']}%" }]
    }

    @total_rows = Branch.count(:all, search_obj)
    @rows = Branch.page(dt[:page]).per(dt[:per_page]).find(:all, search_obj)
  end