title: Nested class from a string
body: <p>I want to call a method on a class in the namespace of <code>Publishers</code>, such as <code>Publishers::Vk</code>, where the nested part is expressed as a string like <code>provider_name = 'Vk'</code>. I did something like that:</p>
  
  <pre><code>send("Publishers::#{provider_name}.new(#{@photo})")
  </code></pre>
  
  <p>I get an exception:</p>
  
  <pre><code>undefined method `Publishers::Vk.new(#&lt;Photo:0x000000085e5440&gt;)' for #&lt;PhotoPublisher:0x00000008616c98&gt;
  </code></pre>
  
  <p>How can I implement this functionality?</p>