json_codable

JSON parsing, validation, and schema generation.

Usage

Parsing & Validation (JsonObject)

JsonObject supports two parsing modes: Accumulated Validation (json.parse) and Fail-Fast (direct constructor).

import 'dart:convert';
import 'package:json_codable/json_codable.dart';

class CreateUserDto {
  CreateUserDto.fromJson(JsonObject json)
      : name = json.string('name', rules: [.length(min: 2)]),
        email = json.string('email', rules: [.email()]),
        age = json.integerOrNull('age', rules: [.range(min: 18)]);

  final String name;
  final String email;
  final int? age;
}

final jsonString = '{"name": "A", "email": "invalid"}';
final jsonMap = jsonDecode(jsonString) as Map<String, Object?>;
final json = JsonObject(jsonMap);

// Accumulated Validation: collects ALL field errors before throwing
try {
  final user = json.parse(CreateUserDto.fromJson);
} on ValidationErrors catch (error) {
  print(error.toJson()); // Contains errors for both 'name' and 'email'
}

// Fail-Fast: throws immediately on the first encountered error
try {
  final user = CreateUserDto.fromJson(json);
} on ValidationErrors catch (error) {
  print(error.toJson()); // Contains only the first error ('name')
}

Serialization (ToJson)

Implement ToJson for DTOs and models that export to JSON maps:

class UserDto implements ToJson {
  UserDto({required this.id, required this.name});

  final String id;
  final String name;

  @override
  Map<String, Object?> toJson() => {
    'id': id,
    'name': name,
  };
}

Schema Generation

Generate JSON Schema documents directly from fromJson mappers or builder callbacks:

class CreateUserDto {
  // ...
  static final Schema schema = JsonObject.schema(
    CreateUserDto.fromJson,
    title: 'CreateUserDto',
  );
}