title: Best way to convert hash keys to array only if their values are set to true
body: <p>I'm trying to find an elegant and compact way to convert hash keys into array that contains only those that have true as value</p>
  
  <pre><code>example = {"foo" =&gt; true, "bar" =&gt; false, "baz" =&gt; true}
  </code></pre>
  
  <p>become </p>
  
  <pre><code>example = ["foo", "baz"]
  </code></pre>