当json属性可能存在也可能不存在时，如何将其导入dart对象

dependencies:
  json_annotation: ^4.0.0

dev_dependencies:
  build_runner: ^2.0.0
  json_serializable: ^4.0.0

import 'package:json_annotation/json_annotation.dart';

part 'your_class_name.g.dart';

@JsonSerializable()
class YourClassName {
  final String? property1;
  final int? property2;
  // ...

  YourClassName({this.property1, this.property2 /* ... */});

  factory YourClassName.fromJson(Map<String, dynamic> json) =>
      _$YourClassNameFromJson(json);

  Map<String, dynamic> toJson() => _$YourClassNameToJson(this);
}

flutter pub run build_runner build

import 'dart:convert';

YourClassName yourObject = YourClassName.fromJson(jsonDecode(yourJsonString));