Hi, I have a problem passing a params value from a form to the model, seems that the value arrives as null !

#User should provide a valid PIN code in the 'card' field
#PIN codes are stored in a table called Cards (each card has a PIN and a Serial number)
#The entered pin code should be verified against the pin codes stored in the Cards table, if not available #registration should fail.


#Viewer

<h2>Signup</h2>
<%= error_messages_for :user %>
<% form_for :user, :url => users_path do |f| -%>
  <p>Username:<br /><%= f.text_field :username, :size => 25 %></p>
  <p>Email:<br /><%= f.text_field :email, :size => 25 %></p>
  <p>Password:<br /><%= f.password_field :password, :size => 25 %></p>
  <p>Password Confirmation:<br />
  <%= f.password_field :password_confirmation, :size => 25 %></p>
  <p>Mobile Number:<br /> <%= f.text_field :mobile_number, :size => 13%></p>
  <p>Pin Code:<br /> <%= f.text_field :card, :size => 13%></p>

  <%= submit_tag 'Sign Up' %>
<% end -%>

#Model

 def self.available_pin?(card)
    Card.find_by_pin(card) ? true : false
  end

#Controller

  def create
     if User.available_pin?(params[:card])

      @user = User.new(params[:user])
      if @user.save
        self.logged_in_user = @user
        flash[:notice] = "Your account has been created."
        redirect_to messages_url
      else
        render :action => 'new'
      end
    else
      flash[:notice] = "PIN is wrong"

    end
  end