How to parse a complex JSON file in Flutter - json

Question

I'm having a really complex JSON file to parse:
{
"adult": false,
"backdrop_url": "https://image.tmdb.org/t/p/w500/gLbBRyS7MBrmVUNce91Hmx9vzqI.jpg",
"belongs_to_collection": {
"id": 230,
"name": "The Godfather Collection",
"poster_url": "https://image.tmdb.org/t/p/w200/sSbkKCHtIEakht5rnEjrWeR2LLG.jpg",
"backdrop_url": "https://image.tmdb.org/t/p/w500/3WZTxpgscsmoUk81TuECXdFOD0R.jpg"
},
"budget": 13000000,
"genres": [
"Drama",
"Crime"
],
"homepage": null,
"id": 240,
"imdb_id": "tt0071562",
"original_language": "en",
"original_title": "The Godfather: Part II",
"overview": "In the continuing saga of the Corleone crime family, a young Vito Corleone grows up in Sicily and in 1910s New York. In the 1950s, Michael Corleone attempts to expand the family business into Las Vegas, Hollywood and Cuba.",
"popularity": 17.578,
"poster_url": "https://image.tmdb.org/t/p/w200/bVq65huQ8vHDd1a4Z37QtuyEvpA.jpg",
"production_companies": [
{
"id": 4,
"logo_url": "https://image.tmdb.org/t/p/w200/fycMZt242LVjagMByZOLUGbCvv3.png",
"name": "Paramount",
"origin_country": "US"
},
{
"id": 536,
"logo_url": null,
"name": "The Coppola Company",
"origin_country": ""
}
],
"production_countries": [
{
"iso_3166_1": "US",
"name": "United States of America"
}
],
"release_date": "1974-12-20",
"revenue": 102600000,
"runtime": 200,
"spoken_languages": [
{
"iso_639_1": "en",
"name": "English"
},
{
"iso_639_1": "it",
"name": "Italiano"
},
{
"iso_639_1": "la",
"name": "Latin"
},
{
"iso_639_1": "es",
"name": "Español"
}
],
"status": "Released",
"tagline": "I don't feel I have to wipe everybody out, Tom. Just my enemies.",
"title": "The Godfather: Part II",
"video": false,
"vote_average": 8.5,
"vote_count": 4794
}
And this is my class for parsing:
class movieDetails {
bool? adult;
String? backdropUrl;
Null? belongsToCollection;
int? budget;
List<String>? genres;
Null? homepage;
int? id;
String? imdbId;
String? originalLanguage;
String? originalTitle;
String? overview;
double? popularity;
String? posterUrl;
List<ProductionCompanies>? productionCompanies;
List<ProductionCountries>? productionCountries;
String? releaseDate;
int? revenue;
int? runtime;
List<SpokenLanguages>? spokenLanguages;
String? status;
String? tagline;
String? title;
bool? video;
double? voteAverage;
int? voteCount;
movieDetails(
{this.adult,
this.backdropUrl,
this.belongsToCollection,
this.budget,
this.genres,
this.homepage,
this.id,
this.imdbId,
this.originalLanguage,
this.originalTitle,
this.overview,
this.popularity,
this.posterUrl,
this.productionCompanies,
this.productionCountries,
this.releaseDate,
this.revenue,
this.runtime,
this.spokenLanguages,
this.status,
this.tagline,
this.title,
this.video,
this.voteAverage,
this.voteCount});
movieDetails.fromJson(Map<String, dynamic> json) {
adult = json['adult'];
backdropUrl = json['backdrop_url'];
belongsToCollection = json['belongs_to_collection'];
budget = json['budget'];
genres = json['genres'].cast<String>();
homepage = json['homepage'];
id = json['id'];
imdbId = json['imdb_id'];
originalLanguage = json['original_language'];
originalTitle = json['original_title'];
overview = json['overview'];
popularity = json['popularity'];
posterUrl = json['poster_url'];
if (json['production_companies'] != null) {
productionCompanies = <ProductionCompanies>[];
json['production_companies'].forEach((v) {
productionCompanies!.add(new ProductionCompanies.fromJson(v));
});
}
if (json['production_countries'] != null) {
productionCountries = <ProductionCountries>[];
json['production_countries'].forEach((v) {
productionCountries!.add(new ProductionCountries.fromJson(v));
});
}
releaseDate = json['release_date'];
revenue = json['revenue'];
runtime = json['runtime'];
if (json['spoken_languages'] != null) {
spokenLanguages = <SpokenLanguages>[];
json['spoken_languages'].forEach((v) {
spokenLanguages!.add(new SpokenLanguages.fromJson(v));
});
}
status = json['status'];
tagline = json['tagline'];
title = json['title'];
video = json['video'];
voteAverage = json['vote_average'];
voteCount = json['vote_count'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['adult'] = this.adult;
data['backdrop_url'] = this.backdropUrl;
data['belongs_to_collection'] = this.belongsToCollection;
data['budget'] = this.budget;
data['genres'] = this.genres;
data['homepage'] = this.homepage;
data['id'] = this.id;
data['imdb_id'] = this.imdbId;
data['original_language'] = this.originalLanguage;
data['original_title'] = this.originalTitle;
data['overview'] = this.overview;
data['popularity'] = this.popularity;
data['poster_url'] = this.posterUrl;
if (this.productionCompanies != null) {
data['production_companies'] =
this.productionCompanies!.map((v) => v.toJson()).toList();
}
if (this.productionCountries != null) {
data['production_countries'] =
this.productionCountries!.map((v) => v.toJson()).toList();
}
data['release_date'] = this.releaseDate;
data['revenue'] = this.revenue;
data['runtime'] = this.runtime;
if (this.spokenLanguages != null) {
data['spoken_languages'] =
this.spokenLanguages!.map((v) => v.toJson()).toList();
}
data['status'] = this.status;
data['tagline'] = this.tagline;
data['title'] = this.title;
data['video'] = this.video;
data['vote_average'] = this.voteAverage;
data['vote_count'] = this.voteCount;
return data;
}
}
class ProductionCompanies {
int? id;
String? logoUrl;
String? name;
String? originCountry;
ProductionCompanies({this.id, this.logoUrl, this.name, this.originCountry});
ProductionCompanies.fromJson(Map<String, dynamic> json) {
id = json['id'];
logoUrl = json['logo_url'];
name = json['name'];
originCountry = json['origin_country'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['logo_url'] = this.logoUrl;
data['name'] = this.name;
data['origin_country'] = this.originCountry;
return data;
}
}
class ProductionCountries {
String? iso31661;
String? name;
ProductionCountries({this.iso31661, this.name});
ProductionCountries.fromJson(Map<String, dynamic> json) {
iso31661 = json['iso_3166_1'];
name = json['name'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['iso_3166_1'] = this.iso31661;
data['name'] = this.name;
return data;
}
}
class SpokenLanguages {
String? iso6391;
String? name;
SpokenLanguages({this.iso6391, this.name});
SpokenLanguages.fromJson(Map<String, dynamic> json) {
iso6391 = json['iso_639_1'];
name = json['name'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['iso_639_1'] = this.iso6391;
data['name'] = this.name;
return data;
}
}
Since I'm getting this JSON from the internet, here's the fetching method:
Future<movieDetails> fetchDetails() async {
final response = await http.get(Uri.parse(url)); //url: just a string containing the website's URL
if (response.statusCode == 200){
return compute(parseDetails, response.body);
}
else{
throw Exception('Failed!');
}
}
Everything seems okay from here, but then I have literally no idea how to do the parseDetails function. How should I do it? This JSON file is too complex for me to handle.

Answer 1

Is there any reason you're using compute to parse the JSON file? The file you provided seems to have reasonable length and won't block the main isolate (unless the file is much bigger than what you provided, where compute might be appropriate)
Your code will be something like this (will parse the JSON response in the main isolate). For more details see the official documentation about JSON. Also a tip, follow the dart naming convention PascalCase for classes (MovieDetails instead of movieDetails)
Future<movieDetails> fetchDetails() async {
final response = await http.get(Uri.parse(url)); //url: just a string containing the website's URL
if (response.statusCode == 200){
Map<String, dynamic> movieDetailsMap = jsonDecode(response.body);
return movieDetails.fromJson(movieDetailsMap);
}
else{
throw Exception('Failed!');
}
}

Answer 2

movieDetails parseDetails(String responseBody) {
final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
return movieDetails.fromJson(parsed);
}