title: How do I create a new model, related to an existing model, using STI?
body: <p>If I have the following models, which use STI:</p>
  
  <pre><code># Organization Model
  class Organization &lt; ActiveRecord::Base
    has_many :questions
    has_many :answers, :through =&gt; :questions
  end
  
  # Base Question Model
  class Question &lt; ActiveRecord::Base
    belongs_to :organization
    has_many :answers
  end
  
  # Subclass of Question
  class TextQuestion &lt; Question
  
  end
  
  # Subclass of Question
  class CheckboxQuestion &lt; Question
  
  end
  </code></pre>
  
  <p>What is the correct way to build a new object that is a particular type of <code>Question</code> <strong>and</strong> also relates to <code>Organization</code>? Or in other words, if I have an organization, and I want that organization to have a new <code>CheckboxQuestion</code>, can I use the regular builder methods?</p>
  
  <p>For example, I was expecting to be able to do:</p>
  
  <pre><code>org = Organization.last
  org.text_questions.build(:question_text =&gt; "What is your name?")
  </code></pre>
  
  <p>... but this gives me an <code>NoMethodError: undefined method text_questions</code>  error.</p>