title: Rails, has_many and joins
body: <p>I have three models, User, Type and TypeDescription, and as you can see below, each User may have many types, but each type has only one description. So as optimization, 
  I thought each TypeDescription should be joined with Type via JOIN in sql, so I used default_scope and defined join, and that works when I get type via Type.find( id ), but when I use user = User.find( 1 ), each type in user.types doesn't have data from TypeDescription, because default_scope just adds defined options to methods like find, all etc. So what I'm looking for is solution to have this work in my situation, so what I want is, when I get certain or all users, I want to have all User's types and each type should have data from TypeDescription.</p>
  
  <p>so, code is:</p>
  
  <pre><code>class User
    has_many :types
  end
  
  class Type
    has_one :type_description
  
    default_scope :joins =&gt; :type_description
  end
  
  class TypeDescription
    belongs_to :type
  end
  </code></pre>
  
  <p>Thanks!</p>