how to return json List using flutter - flutter

Question

i want to return json object list but i dont know how
i'm using the sample doc from flutter the
here is my code
Future<Album> fetchAlbum() async {
final response =
await http.get('https://vpic.nhtsa.dot.gov/api/vehicles/getmodelsformake/honda?format=json');
if (response.statusCode == 200) {
// If the server did return a 200 OK response,
// then parse the JSON.
return Album.fromJson(jsonDecode(response.body));
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
throw Exception('Failed to load album');
}
}
class Album {
final String userId;
final List <String> Cm;
Album({this.userId, this.Cm});
factory Album.fromJson(Map<String, dynamic> json) {
return Album(
userId: json['Results'][0]['Make_Name'],
Cm: for( var i = 0 ; i < json['Count']; i++ ) {
Cm.add(json['Results'][i]['Make_Name']);
}
);
}
}
the error in Cm: for... line

Answer 1

In your code snippet you did not created a class to refer Results list. Try bellow code snippet.
import 'dart:convert';
import 'package:http/http.dart' as http;
Future<Album> fetchAlbum() async {
final response = await http.get(
'https://vpic.nhtsa.dot.gov/api/vehicles/getmodelsformake/honda?format=json');
if (response.statusCode == 200) {
return Album.fromJson(jsonDecode(response.body));
} else {
throw Exception('Failed to load album');
}
}
class Album {
int count;
String message;
String searchCriteria;
List<Results> results;
Album({this.count, this.message, this.searchCriteria, this.results});
Album.fromJson(Map<String, dynamic> json) {
count = json['Count'];
message = json['Message'];
searchCriteria = json['SearchCriteria'];
if (json['Results'] != null) {
results = new List<Results>();
json['Results'].forEach((v) {
results.add(new Results.fromJson(v));
});
}
}
}
class Results {
int makeID;
String makeName;
int modelID;
String modelName;
Results({this.makeID, this.makeName, this.modelID, this.modelName});
Results.fromJson(Map<String, dynamic> json) {
makeID = json['Make_ID'];
makeName = json['Make_Name'];
modelID = json['Model_ID'];
modelName = json['Model_Name'];
}
}

Answer 2

As the for-loop is not returning the list to the cm field, you may try using .map to do the mapping and return it.
Cm: json['Results'].map((e)=>e['Make_Name']).toList()

Answer 3

First off, Flutter is a Framework for Dart language, so you don't need Flutter to run that code. Run code below on console:
import 'dart:convert';
import 'package:http/http.dart' as http;
class NetService {
static Future fetchJsonData(String url) {
return
http.get(url)
.then((response) => response?.statusCode == 200 ? jsonDecode(response.body) : null)
.catchError((err) => print(err));
}
static Future<void> fetchCarModels() {
return
fetchJsonData('https://vpic.nhtsa.dot.gov/api/vehicles/getmodelsformake/honda?format=json')
.then((response) {
if (response != null) {
final Map<String, dynamic> data = response;
print('''
Count : ${data["Count"]}
Message : ${data["Message"]}
Search Criteria : ${data["SearchCriteria"]}
Models :
${(data["Results"] as List)?.fold<String>("", (m, e) => m + (e as Map<String, dynamic>)["Model_Name"] + ", ")}
'''
);
}
})
.catchError((err) => print(err));
}
}
void main(List<String> arguments) async {
await NetService.fetchCarModels();
}