wb = xlsx_package.workbook
wb.add_worksheet(name: 'registrations') do |sheet|
  bold_style = wb.styles.add_style(b: true)
  row = ['Attended', 'Name', 'Nickname', 'Affilιation', 'Email', 'Arrival', 'Departure']

  @conference.questions.each do |question|
    row << question.title
  end

  sheet.add_row row, :style => bold_style

  @registrations.each do |registration|
    row = []
    row << ( registration.attended ? 'X' : '' )
    row << registration.name
    row << registration.nickname
    row << registration.affiliation
    row << registration.email
    row << registration.arrival.to_s
    row << registration.departure.to_s
    @conference.questions.each do |question|
      qa = registration.qanswers.find_by(question: question)
      answer = ( qa ? qa.answer.title : '' )

      row << answer
    end

    sheet.add_row row
  end
end