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POTo Interface or Not?: Creating a polymorphic model relationship in Ruby on Rails dynamically
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  1. POTo Interface or Not?: Creating a polymorphic model relationship in Ruby on Rails dynamically
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    copied!<p>Please bear with me for a moment as I try to explain exactly what I would like to achieve.</p> <p>In my Ruby on Rails application I have a model called Page. </p> <p>It represents a web page.</p> <p>I would like to enable the user to arbitrarily attach components to the page. Some examples of "components" would be Picture, PictureCollection, Video, VideoCollection, Background, Audio, Form, Comments.</p> <p>Currently I have a direct relationship between Page and Picture like this:</p> <pre><code>class Page &lt; ActiveRecord::Base has_many :pictures, :as =&gt; :imageable, :dependent =&gt; :destroy end class Picture &lt; ActiveRecord::Base belongs_to :imageable, :polymorphic =&gt; true end </code></pre> <p>This relationship enables the user to associate an arbitrary number of Pictures to the page. Now if I want to provide multiple collections i would need an additional model:</p> <pre><code>class PictureCollection &lt; ActiveRecord::Base belongs_to :collectionable, :polymorphic =&gt; true has_many :pictures, :as =&gt; :imageable, :dependent =&gt; :destroy end </code></pre> <p>And alter Page to reference the new model:</p> <pre><code>class Page &lt; ActiveRecord::Base has_many :picture_collections, :as =&gt; :collectionable, :dependent =&gt; :destroy end </code></pre> <p>Now it would be possible for the user to add any number of image collections to the page.</p> <p>However this is still very static in term of the :picture_collections reference in the Page model. If I add another "component", for example :video_collections, I would need to declare another reference in page for that component type. </p> <p>So my question is this:</p> <p>Do I need to add a new reference for each component type, or is there some other way? In Actionscript/Java I would declare an interface Component and make all components implement that interface, then I could just have a single attribute :components which contains all of the dynamically associated model objects.</p> <p>This is Rails, and I'm sure there is a great way to achieve this, but its a tricky one to Google. Perhaps you good people have some wise suggestions. Thanks in advance for taking the time to read and answer this.</p>
 

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