Question

So perhaps I’ve found a bug in Rails 3.1.1, or else I don’t understand if Rails 3.1(.1) has changed in some way from Rails 3.0.10 with Nested Resources, Polymorphic associations, and/or routing…

Under Rails 3.0.10 the following works fine, but under Rails 3.1.1 it doesn’t!

These are my models:

class Picture < ActiveRecord::Base
  belongs_to :imageable, :polymorphic => true
end

class Employee < ActiveRecord::Base
  has_many :pictures, :as => :imageable
end

class Product < ActiveRecord::Base
  has_many :pictures, :as => :imageable
end

My routes.rb:

resources :employees do
  resources :pictures
end
resources :products do
  resources :pictures
end

My controller:

class PicturesController < ApplicationController
  def index
    @imageable = find_imageable
    @pictures = @imageable.pictures
  end

  private
  def find_imageable
    params.each do |name, value|
      if name =~ /(.+)_id$/
        return $1.classify.constantize.find(value)
      end
    end
    nil
  end
end

My app/views/pictures/index.html.erb:

<% form_for [@imageable, Picture.new] do |f| %>
    <p><%= f.submit "Add picture" %></p>
<% end %>

I generated the apps with rails new poly -T (for Rails 3.1.1 and for Rails 3.0.10).

I used standard scaffold commands: rails g scaffold Employee name:string, rails g scaffold Product title:string and rails g scaffold Picture caption:string imageable_id:integer imageable_type:string and then migrating, of course.

When hitting the index form (/employees first to create an employee with id == 1; then /employees/1/pictures) I get a blank form (no button appears) on Rails 3.1.1, and a form with the submit button on it, on Rails 3.0.10…

Any ideas if I’m doing something wrong in Rails 3.1.1, or have I really found a bug (I doubt it–I’m sure I’m doing something stupid!)?

Answer 1

In the line:

<% form_for [@imageable, Picture.new] do |f| %>

You are missing the = after the <%. The line should be

#notice the = symbol:
<%= form_for [@imageable, Picture.new] do |f| %>

The older style <% syntax for form_for, field_for etc., was deprecated and scheduled for removal in 3.1, if I remember correctly.