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POForeign Keys and Multi Model forms in Rails 2.3 - Bug or feature?
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  1. POForeign Keys and Multi Model forms in Rails 2.3 - Bug or feature?
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    copied!<p>I am playing with making a blog. I would like to have several types of entries (a link to an interesting site + brief comment, a traditional blog post with title and body text, a picture... you get the idea).</p> <p>The idea seemed straight forward. An entry table/model with a the few details common to all those types (creation time and a little teaser/preview text or something), and then a table/model for each type of entry I would like that will reference the entry table/model.</p> <p>I set up my app according to <a href="http://stream.btucker.org/post/93887650/accepts-nested-attributes-for-fields-for" rel="nofollow noreferrer">this great tutorial</a> for the new Multi model form stuff in 2.3. </p> <pre><code>class Link &lt; ActiveRecord::Base has_one :entry accepts_nested_attributes_for :entry attr_accessible :url, :description, :title, :entry_attributes end class Entry &lt; ActiveRecord::Base belongs_to :link, :dependent =&gt; :destroy #adding more types later end </code></pre> <p>From Links_Controller. Creating a new link type entry:</p> <pre><code>def new @link = Link.new() @link.build_entry respond_to do |format| format.html # new.html.erb format.xml { render :xml =&gt; @link } end end </code></pre> <p>And the view form:</p> <pre><code>&lt;% form_for(@link) do |f| %&gt; &lt;%= f.error_messages %&gt; &lt;p&gt; &lt;%= f.label :title %&gt;&lt;br /&gt; &lt;%= f.text_field :title %&gt; &lt;/p&gt; &lt;p&gt; &lt;%= f.label :url %&gt;&lt;br /&gt; &lt;%= f.text_field :url %&gt; &lt;/p&gt; &lt;p&gt; &lt;%= f.label :description %&gt;&lt;br /&gt; &lt;%= f.text_field :description %&gt; &lt;/p&gt; &lt;% f.fields_for :entry do |e| %&gt; &lt;%= e.label :teaser %&gt;&lt;br /&gt; &lt;%= e.text_field :teaser %&gt; &lt;%= e.text_field(:controller_name, :value =&gt; params[:controller].to_s) %&gt; &lt;% end %&gt; &lt;p&gt; &lt;%= f.submit 'Create' %&gt; </code></pre> <p>I am storing the controller name just so I can list entries but refer to the proper controller to display. Although it appears to work (the multi model form is submitted and a row appears in the table for each of the models involved) the foreign key field is null for all the entries. In the database I get:</p> <pre><code>mysql&gt; select * from links; +----+------------+------------------+---------------------+-------------+ | id | entries_id | title | url | description | +----+------------+------------------+---------------------+-------------+ | 10 | NULL | Snazzy website | www.somewebsite.com | Cool site | | 11 | NULL | Snazzy website | www.somewebsite.com | Cool site | | 12 | NULL | Snazzy website | www.somewebsite.com | Cool site | | 13 | NULL | Snazzy website 2 | www.ab21e312e3c.com | Description | | 14 | NULL | fk_test | fk_test | fk_test | mysql&gt; select * from entries; +----+-----------------+------------------------+---------------------+--------- ------------+ | id | controller_name | teaser | created_at | updated_ at | +----+-----------------+------------------------+---------------------+--------- ------------+ | 10 | links | Check it out | 2009-08-11 09:06:47 | 2009-08- 11 09:06:47 | | 11 | links | Check it out | 2009-08-11 09:08:49 | 2009-08- 11 09:08:49 | | 12 | links | Check it out | 2009-08-11 09:09:04 | 2009-08- 11 09:09:04 | | 13 | links | This is interesting... | 2009-08-11 09:27:29 | 2009-08- 11 09:27:29 | | 14 | links | fk_test | 2009-08-11 20:42:26 | 2009-08- 11 20:42:26 | +----+-----------------+------------------------+---------------------+--------- ------------+ </code></pre> <p>This lack of foreign keys is making retrieval difficult, since it usually relies on the FK values. A couple of questions come out of this:</p> <ol> <li><p>I know DHH writes off DB constraints as business logic that conceptually belongs in the model, so is this how its supposed to work or did I do something wrong? </p></li> <li><p>Should I figure out a way to grab data based on the fact that the id is the same in both the entries table and the links table?</p></li> <li><p>Is there a better way to do what I am attempting?</p></li> </ol>
 

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