title: Declaring a Type variable that must be a subclass - Dart
body: <p>Kotlin code:</p>
  <pre><code>Class&lt;? extends Model&gt; someType();
  </code></pre>
  <p>I want to do the equivalent in Dart where I can <strong>declare</strong> a variable that stores a class that must extend from the Model class.</p>
  <p>So far, I only know how to declare a variable that stores a generic class in a Dart variable via:</p>
  <pre><code>Type someType; 
  </code></pre>
  <p>But I want &quot;someType&quot; to only be Types/Classes that extend from the Model class.</p>