Rails, syntax error?
<p>I'm following this tutorial to create a messaging system in rails. 
<a href="https://medium.com/@danamulder/tutorial-create-a-simple-messaging-system-on-rails-d9b94b0fbca1#.lhwzqr92b" rel="nofollow">https://medium.com/@danamulder/tutorial-create-a-simple-messaging-system-on-rails-d9b94b0fbca1#.lhwzqr92b</a></p>

<p>My main issue now is that I'm getting a syntax error <code>unexpected '?'</code> related to the following scope validation in my Conversation model:</p>

<pre><code>  scope :between, -&gt; (sender_id,recipient_id) do
  where("(conversations.sender_id = ? AND conversations.recipient_id = ? ) OR (conversations.sender_id = ? AND conversations.recipient_id = ? )", sender_id,recipient_id, recipient_id, sender_id)
  end
</code></pre>

<p>It's supposed to check if a conversation between two users already exists so we can make sure only a conversation exists between 2 users.</p>

<p>I've been trying fiddling with the code taking out some parenthesis and googling only gives me general answers. I'm going crazy here. Could someone help to point out the syntax error?</p>