Polymorphic model, Forms and AssociationTypeMismatch

Question

i have two models, Content and Page

class Content < ActiveRecord::Base
   attr_accessible :large_description, :short_description
   belongs_to :contentable , :polymorphic => true
end

class Page < ActiveRecord::Base
   extend FriendlyId
   friendly_id :title, use: [:slugged, :history]
   attr_accessible :active, :menu, :slug, :title, :contents

   validates :title, presence: true

   has_many :contents, as: :contentable
end

this is my simple form to create a new page with contents

<%= form_for([:admin,@page], :html => {:class => "nice custom"}) do |f| %>
  <div class="formRow">
    <%= f.label :title, "Title"%>
    <%= f.text_field :title, :class => 'input-text'%>
  </div>
<%= f.fields_for :contents do |content_form| %>
  <div class="formRow">
   <%= content_form.label :short_description, "Short Description"%>
   <%= content_form.text_area :short_description, :class => 'tinymce expand'%>
  </div>
  <div class="formRow">
    <%= content_form.label :large_description, "Large Description"%>
    <%= content_form.text_area :large_description, :class => 'tinymce expand'%>
  </div>
<% end %>
 <div class="formRow">
    <%= f.submit "Create", :class => 'button small nice blue'%>
 </div>
<% end %>

and finally this is my page controller

class Admin::PagesController < ApplicationController
  layout 'admin'
  def index
    @pages = Page.order("created_at")
  end
  def new
    @page = Page.new
  end
  def create
    @page = Page.new(params[:page])
    if @page.save
     redirect_to page_url
    else
     render :new
     end
  end

  def show
    @page = Page.find(params[:id])
  end

  def destroy
    @page = Page.find(params[:id])
    @page.destroy
    redirect_to page_url
  end
end

i have used a namespace Admin. so the problem is when i send the form, i receive this error and i don't undersand why have a mismatch:

ActiveRecord::AssociationTypeMismatch in Admin::PagesController#create Content(#70150608194420) expected, got Array(#70150590276780)

activerecord (3.2.8) lib/active_record/associations/association.rb:204:in raise_on_type_mismatch' activerecord (3.2.8) lib/active_record/associations/collection_association.rb:308:inblock in replace' activerecord (3.2.8) lib/active_record/associations/collection_association.rb:308:in each' activerecord (3.2.8) lib/active_record/associations/collection_association.rb:308:inreplace' activerecord (3.2.8) lib/active_record/associations/collection_association.rb:41:in writer' activerecord (3.2.8) lib/active_record/associations/builder/association.rb:51:inblock in define_writers' activerecord (3.2.8) lib/active_record/attribute_assignment.rb:94:in block in assign_attributes' activerecord (3.2.8) lib/active_record/attribute_assignment.rb:93:ineach' activerecord (3.2.8) lib/active_record/attribute_assignment.rb:93:in assign_attributes' activerecord (3.2.8) lib/active_record/base.rb:498:ininitialize' app/controllers/admin/pages_controller.rb:13:in new' app/controllers/admin/pages_controller.rb:13:increate' actionpack (3.2.8) lib/action_controller/metal/implicit_render.rb:4:in send_action' actionpack (3.2.8) lib/abstract_controller/base.rb:167:inprocess_action' actionpack (3.2.8) lib/action_controller/metal/rendering.rb:10:in process_action' actionpack (3.2.8) lib/abstract_controller/callbacks.rb:18:inblock in process_action' activesupport (3.2.8) lib/active_support/callbacks.rb:414:in _run__3558390125630086563__process_action__2004224720818030891__callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:405:in__run_callback' activesupport (3.2.8) lib/active_support/callbacks.rb:385:in _run_process_action_callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:81:inrun_callbacks' actionpack (3.2.8) lib/abstract_controller/callbacks.rb:17:in process_action' actionpack (3.2.8) lib/action_controller/metal/rescue.rb:29:inprocess_action' actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:30:in block in process_action' activesupport (3.2.8) lib/active_support/notifications.rb:123:inblock in instrument' activesupport (3.2.8) lib/active_support/notifications/instrumenter.rb:20:in instrument' activesupport (3.2.8) lib/active_support/notifications.rb:123:ininstrument' actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:29:in process_action' actionpack (3.2.8) lib/action_controller/metal/params_wrapper.rb:207:inprocess_action' activerecord (3.2.8) lib/active_record/railties/controller_runtime.rb:18:in process_action' actionpack (3.2.8) lib/abstract_controller/base.rb:121:inprocess' actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in process' actionpack (3.2.8) lib/action_controller/metal.rb:203:indispatch' actionpack (3.2.8) lib/action_controller/metal/rack_delegation.rb:14:in dispatch' actionpack (3.2.8) lib/action_controller/metal.rb:246:inblock in action' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in call' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:indispatch' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:36:in call' journey (1.0.4) lib/journey/router.rb:68:inblock in call' journey (1.0.4) lib/journey/router.rb:56:in each' journey (1.0.4) lib/journey/router.rb:56:incall' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:600:in call' actionpack (3.2.8) lib/action_dispatch/middleware/best_standards_support.rb:17:incall' rack (1.4.1) lib/rack/etag.rb:23:in call' rack (1.4.1) lib/rack/conditionalget.rb:35:incall' actionpack (3.2.8) lib/action_dispatch/middleware/head.rb:14:in call' actionpack (3.2.8) lib/action_dispatch/middleware/params_parser.rb:21:incall' actionpack (3.2.8) lib/action_dispatch/middleware/flash.rb:242:in call' rack (1.4.1) lib/rack/session/abstract/id.rb:205:incontext' rack (1.4.1) lib/rack/session/abstract/id.rb:200:in call' actionpack (3.2.8) lib/action_dispatch/middleware/cookies.rb:339:incall' activerecord (3.2.8) lib/active_record/query_cache.rb:64:in call' activerecord (3.2.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:incall' actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:28:in block in call' activesupport (3.2.8) lib/active_support/callbacks.rb:405:inrun_3479256987463636693_call_4454778504255292268__callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:405:in __run_callback' activesupport (3.2.8) lib/active_support/callbacks.rb:385:in_run_call_callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:81:in run_callbacks' actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:27:incall' actionpack (3.2.8) lib/action_dispatch/middleware/reloader.rb:65:in call' actionpack (3.2.8) lib/action_dispatch/middleware/remote_ip.rb:31:incall' actionpack (3.2.8) lib/action_dispatch/middleware/debug_exceptions.rb:16:in call' actionpack (3.2.8) lib/action_dispatch/middleware/show_exceptions.rb:56:incall' railties (3.2.8) lib/rails/rack/logger.rb:26:in call_app' railties (3.2.8) lib/rails/rack/logger.rb:16:incall' actionpack (3.2.8) lib/action_dispatch/middleware/request_id.rb:22:in call' rack (1.4.1) lib/rack/methodoverride.rb:21:incall' rack (1.4.1) lib/rack/runtime.rb:17:in call' activesupport (3.2.8) lib/active_support/cache/strategy/local_cache.rb:72:incall' rack (1.4.1) lib/rack/lock.rb:15:in call' actionpack (3.2.8) lib/action_dispatch/middleware/static.rb:62:incall' railties (3.2.8) lib/rails/engine.rb:479:in call' railties (3.2.8) lib/rails/application.rb:223:incall' rack (1.4.1) lib/rack/content_length.rb:14:in call' railties (3.2.8) lib/rails/rack/log_tailer.rb:17:incall' rack (1.4.1) lib/rack/handler/webrick.rb:59:in service' /Users/ogonbat/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:138:inservice' /Users/ogonbat/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:94:in run' /Users/ogonbat/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:191:inblock in start_thread'

this are the request parameters

{"utf8"=>"✓", "authenticity_token"=>"g44p+IPxvdm2ouGAE2u2dV/cCKK8uF6G3XLL4z26zrI=", "page"=>{"title"=>"zfdzfdsf", "contents"=>{"short_description"=>"
sdfdsf
", "large_description"=>"
dsfdsf
"}}, "commit"=>"Create"}

thank's in advance for your help

rewritten rewritten · Accepted Answer · 2012-10-15T00:42:03

If the page has_many :contents, then it's strange that params[:page][:contents] is a hash and not an array...

Either fix one or the other end of the incongruence. If you have a has_many realtionship and you want to create a form for it, prepopulate a number of empty items for it in the main object, and iterating over them, generate the corresponding fields.

You can see ALL responses to Nested forms in rails - accessing attribute in has_many relation to get an idea on what you need.

Polymorphic model, Forms and AssociationTypeMismatch

2 Answers