########Viewer

<% form_for :card, :url => {:action => "generate"} do |f| -%>
  <p>Number of cards<br /><%= f.text_field :number_of_cards, :size => 10 %></p>

  <%= submit_tag 'Generate' %>
<% end -%>

############Controller

def generate
  number_of_cards.times do
    pin    = rand(999999999999).to_s.center(12, rand(9).to_s)
    serial = rand(999999999999).to_s.center(12, rand(9).to_s)
    Card.create({:pin => pin, :serial => serial})
  end
end