has_many_polymorphs: Tag could not be preloaded: #<ActiveRecord::Associations::PolymorphicError

rubyonrails-talk
1

Hello there,

I've also posted this problem at the hmp forum @ http://rubyforge.org/forum/forum.php?thread_id=22433&forum_id=16450 but since this group has some higher traffic, maybe the one or another can help me here, too.

I have a little rails (2.0.2) app with very few models so far, one being a user model which has_many text_snippets and also has_many bookmarks. Resources wise, these two are nested under the users .. so callable via /users/1/bookmarks/15 etc.

I ran the hmp tagging generator with the two models Bookmark and Textsnippet which led to this entry in the tag.rb file:

  has_many_polymorphs :taggables,     :from => [:bookmarks, :text_snippets],     :through => :taggings,     :dependent => :destroy,     :skip_duplicates => false,     :parent_extend => proc {       # Defined on the taggable models, not on Tag itself. Return the tagnames associated with this record as a string.       def to_s         self.map(&:name).sort.join(Tag::DELIMITER)       end     }

So far so good. However, when starting the server, this is being logged:

** has_many_polymorphs: rails environment detected ** has_many_polymorphs: loaded ok ** has_many_polymorphs: autoload hook invoked ** has_many_polymorphs: preloading parent model Tag ** has_many_polymorphs: associating Tag.taggables ** has_many_polymorphs: Tag could not be preloaded: #<ActiveRecord::Associations::PolymorphicError: Could not find a valid class for :bookmarks. If it's namespaced, be sure to specify it as :"module/bookmarks" instead.> ** has_many_polymorphs: preloading parent model Tagging ** has_many_polymorphs: autoload hook invoked ** has_many_polymorphs: preloading parent model Tag ** has_many_polymorphs: associating Tag.taggables   SQL (0.028267) SET NAMES 'utf8'   SQL (0.010828) SET SQL_AUTO_IS_NULL=0   Bookmark Columns (0.103882) SHOW FIELDS FROM `bookmarks`   Tagging Columns (0.018256) SHOW FIELDS FROM `taggings`   TextSnippet Columns (0.019460) SHOW FIELDS FROM `text_snippets` ** has_many_polymorphs: preloading parent model Tagging

Now neither the text_snippets nor the bookmarks are taggable (double- checked via console). However, this error is somewhat misleading or ... well.. dunno.. the Bookmark class does in fact exist:

Loading development environment (Rails 2.0.2)

Bookmark.inspect

=> "Bookmark(id: integer, user_id: integer, url: string, title: string, description: text, created_at: datetime, updated_at: datetime)"

I am really kind of confused now where to start digging/looking... tried all I could, double-checked whether bookmarks' files are all correct.. which they are.. but still it ain't working.

Has anyone else come across this somewhere/somehow? Any ideas/ suggestions? :slight_smile:

-J

2

Ok - found it :-/

I have a custom validation in my Bookmark model. This validation is declared in lib/custom_validations.rb ... which is require'ed in environment.rb. Now hmp (the plugin) gets loaded before the custom_validations.rb file is loaded.. and therefore the Bookmark class looks b0rked at that very moment.

Once rails has in fact loaded the custom_validations.rb file, everything works fine at the Bookmark-class level.. but hmp actually isn't.

Hrrmm - what can I do now? I mean... I can't be the only one using custom validations in the lib/ folder in combination with hmp... :-/

-j

3

In Rails 2.x you should be able to use initializers (/config/ initializers + environment) to control the load order. Likely a well- placed 'require' will solve the problem.