Question

I’m having difficulties getting an association to work with simple_form.

I have the following models.

class Product < ActiveRecord::Base
  belongs_to :Retailer
end

and

class Retailer < ActiveRecord::Base
   has_many :Products
end

My form partial (products/_form.html.erb) contains the following

<%= simple_form_for(@product) do |f| %>
...
<% f.input :currency %>
<% f.association :retailer %>
...

It works without the association, but with it I get the following error:

undefined method `retailer_id' for #<Product:0x007ffbe0f7d530>

I’m (obviously) quite new to this, but haven’t been able to work this out.

edit: checked I’d run migrations and they are up-to-date. The Retailer table has an id column!

> Retailer.all
Retailer Load (0.2ms)  SELECT "retailers".* FROM "retailers" 
=> [#<Retailer id: 1, name: "Retailer 1" etc...

chema file:

ActiveRecord::Schema.define(:version => 20120308195055) do

  create_table "alerts", :force => true do |t|
   t.string   "url",        :null => false
   t.datetime "created_at", :null => false
   t.datetime "updated_at", :null => false
  end

  create_table "products", :force => true do |t|
      t.string   "title",                      :null => false
      t.integer  "price_cents", :default => 0, :null => false
      t.string   "currency",                   :null => false
      t.string   "asin",                       :null => false
      t.datetime "created_at",                 :null => false
      t.datetime "updated_at",                 :null => false
  end

    create_table "retailers", :force => true do |t|
      t.string   "name",       :null => false
      t.datetime "created_at", :null => false
      t.datetime "updated_at", :null => false
    end

  end

Answer 1

Since you have belongs_to :Retailer and <% f.association :retailer %> in your model and form for Product respectively, you’ll need to add a retailer_id column to your products table.

You are missing t.references :retailer in your migration file for creating products table.
That is why, I quote you “it works without the association, but with it the error is undefined method 'retailer_id' for #<Product:0x007ffbe0f7d530>“

Yes, the retailers table has an id column but in order to reference a retailer from a product, your products table requires a retailer_id column.