title: Rails 3 validate presence of many columns with custom messages
body: <p>Is there a way to specify many validations like this more concisely?</p>
  
  <pre><code>validates :col_a, :presence =&gt; {:message =&gt; 'col_a cannot be blank'}
  validates :col_b, :presence =&gt; {:message =&gt; 'col_b cannot be blank'}
  validates :col_c, :presence =&gt; {:message =&gt; 'col_c cannot be blank'}
  </code></pre>
  
  <p>I'd settle for a generic message if I had to.</p>