title: Validate presence of one of multiple attributes in rails
body: <p>In an multilingual application, a user can input their Chinese and English names. The user can input either or both, but must input at least one name.</p>
  
  <pre><code>class Person &lt; ActiveRecord::Base
    validates :zh_name, :presence =&gt; true
    validates :en_name, :presence =&gt; true
    validates :fr_name, :presence =&gt; true
  end
  </code></pre>
  
  <p>Since the built-in :validates_presence_of method can only validate both attributes at once, is there a way to validate the presence of at least one of many attributes in rails?</p>
  
  <p>Like a magical, <code>validates_one_of :zh_name, :en_name, :fr_name</code></p>
  
  <p>Thank you in advance,</p>