title: Polymorphism in Dart/Flutter
body: <p>I have a number of classes that all extend <code>StatefulWidget</code>. I want each class to provide its own version of a method <code>bool foo()</code>, so that I can iterate over a collection of objects of these classes, calling <code>foo()</code> on each. What is the best/correct way to do this in Dart/Flutter? Mixins? What would the type of that collection be?</p>