Trivial example of writing to a spreadsheet using a buffer

speadsheet_buffer.rb

require 'spreadsheet'
def speadsheet_with_buffer
  buf = StringIO.new
  book = Spreadsheet::Workbook.new

  sheet = book.create_worksheet :name => "New Worksheet"
  sheet.row(0).concat %w{col_1, col_2, col_3}
  sheet[1,0] = "next row, first column"

  book.write buf

  # using rails 'send_data', send the file in the buffer as the response
  send_data buf.string, type: "application/ms-excel", disposition: "attachment", :filename => "my_new_xls_file.xls"
end