Dart has special syntaxs for nullable variables - the ? symbol, and we translate Option into ? automatically. You may refer to the official doc for more information.

In addition, flutter_rust_bridge also understands the required keyword in Dart: If an argument is not-null, it is marked as required since you have to provide a value. On the other hand, if it is nullable, no required is needed since by Dart's convention a null is there in absence of manually providing a value.


pub struct Element {
    pub tag: Option<String>,
    pub text: Option<String>,
    pub attributes: Option<Vec<Attribute>>,
    pub children: Option<Vec<Element>>,

pub fn parse(mode: String, document: Option<String>) -> Option<Element> { ... }


Future<Element?> handleOptionalStruct({required String mode, String? document});

class Element {
  final String? tag;
  final String? text;
  final List<Attribute>? attributes;
  final List<Element>? children;
  Element({this.tag, this.text, this.attributes, this.children});

Remark: If you are curious about Future, have a look at this.