在Flutter中解析JSON会导致对象字段的空值

if (json['fieldName'] != null) {
  // 解析并使用该字段的值
} else {
  // 字段不存在或值为空
}

var value = json['fieldName'] ?? defaultValue;

dependencies:
  json_annotation: <latest_version>
  # 其他依赖
dev_dependencies:
  build_runner: <latest_version>
  json_serializable: <latest_version>

import 'package:json_annotation/json_annotation.dart';

part 'example_model.g.dart';

@JsonSerializable()
class ExampleModel {
  String fieldName;

  ExampleModel(this.fieldName);

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

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

flutter packages pub run build_runner build

ExampleModel example = ExampleModel.fromJson(json);
var json = example.toJson();