restaurant-ratings-json-serialization.dart

import 'dart:convert';

class Restaurant {
  Restaurant({
    required this.name,
    required this.cuisine,
    this.yearOpened,
    required this.reviews,
  });
  final String name;
  final String cuisine;
  final int? yearOpened;
  final List<Review> reviews;

  factory Restaurant.fromMap(Map<String, dynamic> data) {
    final name = data['name'] as String;
    final cuisine = data['cuisine'] as String;
    final yearOpened = data['yearOpened'] as int?;
    final reviewsData = data['reviews'] as List<dynamic>?;
    final reviews = reviewsData != null
        ? reviewsData.map((reviewData) => Review.fromMap(reviewData)).toList()
        : <Review>[];
    return Restaurant(
      name: name,
      cuisine: cuisine,
      yearOpened: yearOpened,
      reviews: reviews,
    );
  }

  Map<String, dynamic> toMap() {
    return {
      'name': name,
      'cuisine': cuisine,
      if (yearOpened != null) 'yearOpened': yearOpened,
      'reviews': reviews.map((review) => review.toMap()).toList(),
    };
  }
}

class Review {
  Review({required this.score, this.review});
  final double score;
  // nullable - assuming the review may be missing
  final String? review;

  factory Review.fromMap(Map<String, dynamic> data) {
    final score = data['score'] as double;
    final review = data['review'] as String?;
    return Review(score: score, review: review);
  }

  Map<String, dynamic> toMap() {
    return {
      'score': score,
      if (review != null) 'review': review,
    };
  }
}

void main() {
  final jsonData =
      '{"name":"Pizza da Mario","cuisine":"Italian","reviews":[{"score":4.5,"review":"The pizza was amazing!"},{"score":5.0,"review":"Very friendly staff, excellent service!"}]}';
  final parsedJson = json.decode(jsonData);
  final restaurant = Restaurant.fromMap(parsedJson);
  final restaurantData = restaurant.toMap();
  final encoded = json.encode(restaurantData);
  assert(encoded == jsonData);
}