Rails form_for and text_field without model attribute

Question

I'm writing a form for users to register their products with. I already have class User has_many :products and class Product belongs_to :user; attr_accessible :serial_number class Product belongs_to :user; attr_accessible :serial_number . So the idea is that the user enters the serial number in the form and I call @user.products << Product.find_by_serial_number params[:serial_number] or somesuch.

It seemed sensible to add this as a register action to the UsersController :

resources :users do
  member do
    get 'register'
  end
end

And I have the following in register.html.erb :

5:   <%= render 'shared/error_messages' %>
6: 
7:   <%= f.label :serial_number, "Serial number" %>
8:   <%= f.text_field :serial_number %>
9: 
10:   <%= f.submit "Register product" %>
11: <% end %>

This throws the error:

undefined method `serial_number' for #<User:0x000000060b1d40>
extracted source (around line #8):
...

So...a) How do I stop this error? b) Umm...what's going to happen after the submit button is pressed? I'm assuming it'll call the update action (which is also used by the edit form)...should I make that fatter to deal with both possiblities? Or make a new action? (If so, how do I reroute the form to point to that?) c) Error-handling (putting in an invalid serial number) is best handled in the controller, not the model, right?

Thanks.

Answer 1

You can only use the form helper for attributes of the model. In this case you will need to use the full method.

 = label_tag :serial_number, 'Serial number'
 = text_field_tag :serial_number

Answer 2

The error being thrown indicates that there's no method serial_number for the User model... which there isn't. The method is actually attached to the Product model, but the form in register.html.erb is for User . You can resolve this by using a nested form.

First, ensure that User can accept nested attributes for Product :

# app/models/user.rb
has_many :products
accepts_nested_attributes_for :products

Then, make your form into a nested form:

# app/views/users/register.html.erb
<%= form_for(@user) do |f| %>

  <%= f.fields_for :products do |e| %>
    <%= e.label :serial_number, "Serial number" %>
    <%= e.text_field :serial_number %>
  <% end %>

  <%= f.submit "Register product" %>

<% end %>