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POhow to access rails join model attributes when using has_many :through
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  1. POhow to access rails join model attributes when using has_many :through
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    copied!<p>I have a data model something like this:</p> <pre><code># columns include collection_item_id, collection_id, item_id, position, etc class CollectionItem &lt; ActiveRecord::Base self.primary_key = 'collection_item_id' belongs_to :collection belongs_to :item end class Item &lt; ActiveRecord::Base has_many :collection_items has_many :collections, :through =&gt; :collection_items, :source =&gt; :collection end class Collection &lt; ActiveRecord::Base has_many :collection_items, :order =&gt; :position has_many :items, :through =&gt; :collection_items, :source =&gt; :item, :order =&gt; :position end </code></pre> <p>An Item can appear in multiple collections and also more than once in the same collection at different positions.</p> <p>I'm trying to create a helper method that creates a menu containing every item in every collection. I want to use the collection_item_id to keep track of the currently selected item between requests, but I can't access any attributes of the join model via the Item class.</p> <pre><code>def helper_method( collection_id ) colls = Collection.find :all colls.each do |coll| coll.items.each do |item| # !!! FAILS HERE ( undefined method `collection_item_id' ) do_something_with( item.collection_item_id ) end end end </code></pre> <p>I tried this as well but it also fails with ( undefined method `collection_item' )</p> <pre><code>do_something_with( item.collection_item.collection_item_id ) </code></pre> <p>Edit: thanks to serioys sam for pointing out that the above is obviously wrong</p> <p>I have also tried to access other attributes in the join model, like this:</p> <pre><code>do_something_with( item.position ) </code></pre> <p>and:</p> <pre><code>do_something_with( item.collection_item.position ) </code></pre> <p>Edit: thanks to serioys sam for pointing out that the above is obviously wrong</p> <p>but they also fail.</p> <p>Can anyone advise me how to proceed with this?</p> <p>Edit: --------------------></p> <p>I found from online documentation that using has_and_belongs_to_many will attach the join table attributes to the retreived items, but apparently it is deprecated. I haven't tried it yet.</p> <p>Currently I am working on amending my Collection model like this:</p> <pre><code>class Collection &lt; ActiveRecord::Base has_many :collection_items, :order =&gt; :position, :include =&gt; :item ... end </code></pre> <p>and changing the helper to use coll.collection_items instead of coll.items</p> <p>Edit: --------------------></p> <p>I've changed my helper to work as above and it works fine - (thankyou sam)</p> <p>It's made a mess of my code - because of other factors not detailed here - but nothing that an hour or two of re-factoring wont sort out.</p>
 

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