| # isDefined property | |
| bool isDefined | |
| <p>True if the value is <a href="../../package-fidl_fidl/Some-class.md">Some</a> or <a href="../../package-fidl_fidl/None-class.md">None</a>.</p> | |
| ## Implementation | |
| ```dart | |
| bool get isDefined => this is Some || this is None; | |
| ``` | |