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    <p>If the differences are just in the behavior of the class, then I assume it shouldn't be a problem, and this is a good candidate for STI. (Mind you, I've never tried this with so many subclasses.)</p> <p>But, if your 200 STI classes each have some unique attributes, you would need a lot of extra database columns in the master table which would be NULL, 99.5% of the time. This could be very inefficient.</p> <p>To create something like "multiple table inheritance", what I've done before with success was to use a little metaprogramming to associate other tables for the details unique to each class:</p> <pre><code>class SpecificGraph &lt; Graph include SpecificGraphDetail::MTI end class SpecificGraphDetail &lt; ActiveRecord::Base module MTI def self.included(base) base.class_eval do has_one :specific_graph_detail, :foreign_key =&gt; 'graph_id', :dependent =&gt; :destroy delegate :extra_column, :extra_column=, :to =&gt; :specific_graph_detail end end end end </code></pre> <p>The delegation means you can access the associated detail fields as if they were directly on the model instead of going through the <code>specific_graph_detail</code> association, and for all intents and purposes it "looks" like these are just extra columns.</p> <p>You have to trade off the situations where you need to join these extra detail tables against just having the extra columns in the master table. That will decide whether to use STI or a solution using associated tables, such as my solution above.</p>
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    1. POHow many classes is too many? Rails STI
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    1. USAndrew Vit
    1. USAndrew Vit
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    1. POHow many classes is too many? Rails STI
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    1. COThanks for the reply. At this point I do not think we would have many (if any) null values in the database, as the properties are the same, just the values and methods would change. (For instance how it returns the data for the graph to plot). If we do end up with null fields (maybe not this particular instance, but other similar ones) I will certainly keep this in mind.
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      1. USAlan Peabody
    2. COThere's another similar approach in http://stackoverflow.com/questions/1634668/multiple-table-inheritance-vs-single-table-inheritance-in-ruby-on-rails/1634734#1634734
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