title: ActionController::UnknownFormat for respond_with
body: <p>I have returned to my ruby on rails project to find that I am getting:</p>
  
  <pre><code>ActionController::UnknownFormat
  </code></pre>
  
  <p>error for a very simple line of code:</p>
  
  <pre><code>    respond_with(allMatches)
  </code></pre>
  
  <p>The allMatches hash is defined as:</p>
  
  <pre><code>        allMatches = {  "matchesProposed"   =&gt; proposedMatchAndNeedsActionObjects,
                          "matchesReceived"   =&gt; receivedMatchAndNeedsActionObjects,
                          "scheduledMatches"  =&gt; scheduledMatches}
  </code></pre>
  
  <p>I have declared at the class level:</p>
  
  <pre><code>class HomeController &lt; ApplicationController
  
    respond_to :json
  </code></pre>
  
  <p>The code has been functioning just fine, until today - no changes!  Any thoughts?</p>