Question

I’m trying to create a partial template using <%= render “/shopping/coupons/cou” %> . Not really sure where went wrong. Thanks!

This is the error message.

undefined method `model_name' for NilClass:Class

Extracted source (around line #3):
1: <h4> Coupon </h4>
2: 
3: <%= form_for(@coupon, :url => shopping_coupon_path(@coupon)) do |f| %>
4:   <div class="field">
5:     <%= f.label :code %>
6:     <%= f.text_field :code %>

this is my coupons controller

class Shopping::CouponsController < Shopping::BaseController
  def cou
    form_info
  end

  def create
    @coupon = Coupon.find_by_code(params[:coupon][:code])

    if @coupon && @coupon.eligible?(session_order) && update_order_coupon_id(@coupon.id)
      flash[:notice] = "Successfully added coupon code #{@coupon.code}."
      redirect_to shopping_orders_url
    else
      form_info
      flash[:notice] = "Sorry coupon code: #{params[:coupon][:code]} is not valid."
      render :action => 'show'
    end
  end

  private

  def form_info
    @coupon = Coupon.new
  end

  def update_order_coupon_id(id)
    session_order.update_attributes( :coupon_id => id ）                                      
  end
end

Answer 1

@coupon is nil when the view is being rendered.
The problem might be that <%= render "/shopping/coupons/cou" %> does not go through the cou action in the controller thus form_info method does not execute and @coupon does not get assigned a value.

You have to set @coupon in the action which renders the main view (the one which has the <%= render "/shopping/coupons/cou" %> in it).