CSV.generate(options) do |csv|
    columns = %w(name, email_address)
    url = "@example.com"
    all.each do |location|
      csv << location.attributes.values_at(*columns) + [url]
    end
  end

Joe, user1, @example.com
Bob, user2, @example.com

Joe, user1@example.com
Bob, user2@example.com

CSV.generate(options) do |csv|
  domain = "example.com"

  all.each do |location|
    csv << [location.name, "#{location.email_address}@#{domain}"]
  end
end

class Location << ActiveRecord::Base
  def full_email_address
    return "" if self.email_address.blank?

    domain = "example.com" # or save this as a constant in the class
    "#{self.email_address}@#{domain}"
  end
end

CSV.generate(options) do |csv|
  columns = %w{name full_email_address} # add other methods or attributes here

  all.each do |location|
    csv << columns.map{ |moa| location.public_send(moa) }
  end
end

CSV.generate(options) do |csv|
  columns = %w(name, email_address)
  url = "@example.com"
  all.each do |location|
    row = location.attributes.values_at(*columns)
    row[-1] = row[-1] + url
    csv << row
  end
end