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PORuby Datamapper table inheritance with associations
 

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    <p>I started learning <a href="http://datamapper.org/" rel="noreferrer">Datamapper</a> and what I liked about it was that I can write my models with real inheritance.</p> <p>Now I wonder, if it is possible to be more advanced about this:</p> <pre><code>class Event include DataMapper::Resource property :id, Serial property :begin, DateTime property :type, Discriminator end class Talk&lt;Event property :title, String belongs_to :meeting end class Meeting&lt;Event has n, :talks end </code></pre> <p>That code fails to create the <code>:title</code> column for the <code>Talk</code> and obviously, the discriminator column is of little value here, because from a database view, there should be separate tables for both <code>Talk</code> and <code>Meeting</code>.</p> <p>So, in the end, I want <code>Talk</code> and <code>Meeting</code> to share the same properties as defined in <code>Event</code> but with possible additional properties and with a 0..1:n relation (A meeting can have several talks but there are talks without a meeting.) Is there a way to accomplish this without either repeating the column definitions and/or abandoning inheritance?</p> <p><strong>Edit</strong></p> <p>To give another example: The part that I like about the inheritance thing is, that general <code>Event</code>s can be queried separately. So, when I want to know, if there is something at a certain <code>:begin</code> date, I don’t need to look in two or more tables but could just query the <code>Event</code> table. In a way, the following structure could fit my needs.</p> <pre><code>class Event include DataMapper::Resource property :id, Serial property :begin, DateTime end class Talk include DataMapper::Resource property :id, Serial property :title, String belongs_to :event belongs_to :meeting end class Meeting include DataMapper::Resource property :id, Serial belongs_to :event has n, :talks end </code></pre> <p>However, in order to use this, I would need to manually create an <code>Event</code> every time, I want to create or edit a <code>Talk</code>. That is, I can’t do <code>talk.begin</code> or <code>Talk.create(:begin =&gt; Time.now)</code>. Is there a way around this without patching all functions and merging the properties? I don’t want to be reminded of the underlying structure when using the model.</p>
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    1. COWhich type of inheritance do you mean by real inheritance- Single Table Inheritance, Class Table Inheritance, or Concrete Table Inheritance? http://martinfowler.com/eaaCatalog/
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    2. COI mean Ruby class inheritance.
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    3. COWhatever this means table-wise, I don’t care that much about – as long as I can use each Ruby model separately and cast/assign from subclass to parent and back.
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