Hi! 👋 , This is JSON Fields, a package that helps you to work with JSON data.

package:json_fields is a library that generates a class to access the serialized names of the fields in your Dart Object.

Motivation 💪

I have frequently come across situations where I want to store a JSON object in a database, but I don't want to update the entire object every time I make a change.

The only way to get around this was to type out the key/field name in the request or create a static variable within the class. All of this is tedious, prone to typos/incorrect formatting/errors, its not DRY, and can require all developers working on the project to know the DB structure. 😣 😬

package:json_fields leverages package:json_annotation to create the fields class, making a fast addition to your already serialized classes.

Setup 🖥

To configure your project for the latest released version of json_fields see the example.

Example 🧐

Also see the example

In example.dart we have a Person class annotated with @JsonSerializable:

import 'package:json_annotation/json_annotation.dart';

part 'example.g.dart';

@JsonSerializable()
class Person {
  /// The generated code assumes these values exist in JSON.
  final String firstName, lastName;

  /// The generated code below handles if the corresponding JSON value doesn't
  /// exist or is empty.
  final DateTime? dateOfBirth;

  Person({required this.firstName, required this.lastName, this.dateOfBirth});

  /// Connect the generated [_$PersonFields] class to the fields getter.
  static _$PersonFields get fields => _$PersonFields();


  // --- json_serializable ---
  //! fromJson & toJson are not required to use `json_fields`
  //! but they are included here for completeness.

  /// Connect the generated [_$PersonFromJson] function to the `fromJson`
  /// factory.
  factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);

  /// Connect the generated [_$PersonToJson] function to the `toJson` method.
  Map<String, dynamic> toJson() => _$PersonToJson(this);

}

Building creates the corresponding part example.g.dart:

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'example.dart';

// **************************************************************************
// JsonFieldsGenerator
// **************************************************************************

class _$PersonFields {
  const _$PersonFields();
  final String firstName = 'firstName';
  final String lastName = 'lastName';
  final String dateOfBirth = 'dateOfBirth';
}

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

Person _$PersonFromJson(Map<String, dynamic> json) => Person(
      firstName: json['firstName'] as String,
      lastName: json['lastName'] as String,
      dateOfBirth: json['dateOfBirth'] == null
          ? null
          : DateTime.parse(json['dateOfBirth'] as String),
    );

Map<String, dynamic> _$PersonToJson(Person instance) => <String, dynamic>{
      'firstName': instance.firstName,
      'lastName': instance.lastName,
      'dateOfBirth': instance.dateOfBirth?.toIso8601String(),
    };

Accessing the JSON key fields:

{
  // 'firstName': 'John'
  Person.fields.firstName: 'John',
}

Running the code generator 🏃‍♂️

Once you have added the annotations to your code you then need to run the code generator to generate the missing .g.dart generated dart files.

If this file already exists, the json_fields tool will prepend the generated code

In your package directory you can run the following command:

• For Dart: dart run build_runner build

• For Flutter: flutter pub run build_runner build

Annotation values 😎

The only annotation required to use this package is JsonSerializable. When applied to a class (in a correctly configured package), the fields class will be generated when you build. There are three ways to control how code is generated:

1. Setting properties on JsonKey annotating the target field.
2. Set properties on JsonSerializable annotating the target type.
3. Add configuration to build.yaml – more here.

for more information: package:json_serializable