title: Flutter Empty Constructing value
body: <p>When I create an object right now, if that object has missing fields those are set to null. Is it possible to make them non-existent if they are empty? Ex:</p>
  <pre><code>class Example {
    Example({this.username, this.email, this.fullName});
    String username;
    String email;
    String fullName;
  }
  
  Example user = Example(username: &quot;john99&quot;, fullName: &quot;John Doe&quot;);
  // This returns a User(username: &quot;john99&quot;, fullName: &quot;John Doe&quot;, email: null);
  // I would like to have this return the following: User(username: &quot;john99&quot;, fullName: &quot;John Doe&quot;);
  </code></pre>