Question

I’m currently building a data generator. First I want to implement is PESEL (kind of personal ID in Poland based on birth date) generator – I want to enter in form a temporary data with start and end birth date interval – I don’t want to store it in database (or I should I do it?)
Here is my pesel controller:

  def new
    @pesel = Array.new
    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @pesel }
    end
  end

but I’ve got an “undefined method `model_name’ for NilClass:Class” error – is it a good way anyway of solvint this case? I read somewhere that using temporary variables is not with ‘The Ruby Way’ – if my solution is wrong, please suggest the correct one. (e.g pass this vars through cookies? hash? helper method?)

here is the stacktrace(I think):

Started GET "/pesel" for 127.0.0.1 at 2011-12-05 16:18:20 +0100
  Processing by PeselController#new as HTML
Rendered pesel/new.html.erb within layouts/application (1513.9ms)
Completed 500 Internal Server Error in 1793ms

ActionView::Template::Error (undefined method `model_name' for NilClass:Class):
    1: <%= simple_form_for @pesel do |f| %>
    2:   <%= f.input :date_of_birth, :as => :date, :start_year => Date.today.year - 90,
    3:                                 :end_year => Date.today.year - 12, :discard_day => true,
    4:                                 :order => [:month, :year] %>
  app/views/pesel/new.html.erb:1:in `_app_views_pesel_new_html_erb__708648673_90148530'
  app/controllers/pesel_controller.rb:7:in `new'

Rendered /home/ofca/.rvm/gems/ruby-1.9.2-p290/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/_trace.erb (5.6ms)
Rendered /home/ofca/.rvm/gems/ruby-1.9.2-p290/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (4.0ms)
Rendered /home/ofca/.rvm/gems/ruby-1.9.2-p290/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (17.6ms)

Answer 1

form_for assumes certain properties exist for the object you pass it, such as model_name.

1. Instead of using form_for @pesel, just use form_tag and the related _tag methods.
2. Use a Pesel model. Models are not tables, and your model doesn’t have to write anything to the database. Just don’t inherit from ActiveRecord, but do provide a model_name and any other fields the form_for helper expects.