How to parse json array into list in dart? - json

Question

As for the script below, I have two different json for single record and multiple record as a list. I can parse the single data using the Person class. For the json with a list, I'm using ther PersonList class but I'm getting an error because the json key result is not needed anymore. Is there a way to parse the list without changing the Person class? Or should I not use the PersonList class and just create a List<Person>?
I saw this example but its only working if the json is a whole list like this
var jsonResponse = convert.jsonDecode(rawJsonMulti) as List;
return jsonResponse.map((p) => Person.fromJson(p).toList();
Can you show me how to use the above script using my json. Thanks.
import 'dart:convert';
void main() {
String rawJsonMulti = '{"result": [{"name":"Mary","age":30},{"name":"John","age":25}]}';
String rawJsonSingle = '{"result": {"name":"Mary","age":30}}';
// Working for non list json
// final result = json.decode(rawJsonSingle);
// var obj = Person.fromJson(result);
// print(obj.name);
final result = json.decode(rawJsonMulti);
var obj = PersonList.fromJson(result);
print(obj.listOfPerson[0].name);
}
class PersonList {
final List<Person> listOfPerson;
PersonList({this.listOfPerson});
factory PersonList.fromJson(Map<String, dynamic> json) {
var personFromJson = json['result'] as List;
List<Person> lst =
personFromJson.map((i) => Person.fromJson(i)).toList();
return PersonList(listOfPerson: lst);
}
}
class Person {
String name;
int age;
//will only work on result is not a list
Person({this.name, this.age});
factory Person.fromJson(Map<String, dynamic> json) {
return Person(name: json['result']['name'],
age: json['result']['age']);
}
// This will work on json with list but not in single
// factory Person.fromJson(Map<String, dynamic> json) {
// return Person(name: json['name'],
// age: json['age']);
// }
}

Answer 1

If you convert the dynamic to a List<dynamic> you can map each element in the jsonDecoded list.
Example:
import 'dart:convert';
final decodedJson = jsonDecode(rawJsonMulti) as List<dynamic>;
final personList = decodedJson
.map((e) => Person.fromJson(
e as Map<String, dynamic>))
.toList();
return PersonList(listOfPerson: personList);
```

Answer 2

Try take a look at this solution where I have fixed your code:
import 'dart:convert';
void main() {
const rawJsonMulti =
'{"result": [{"name":"Mary","age":30},{"name":"John","age":25}]}';
const rawJsonSingle = '{"result": {"name":"Mary","age":30}}';
final resultMulti = json.decode(rawJsonMulti) as Map<String, dynamic>;
final personListMulti = PersonList.fromJson(resultMulti);
print(personListMulti.listOfPerson[0]); // Mary (age: 30)
print(personListMulti.listOfPerson[1]); // John (age: 25)
final resultSingle = json.decode(rawJsonSingle) as Map<String, dynamic>;
final personListSingle = PersonList.fromJson(resultMulti);
print(personListSingle.listOfPerson[0]); // Mary (age: 30)
}
class PersonList {
final List<Person> listOfPerson;
PersonList({this.listOfPerson});
factory PersonList.fromJson(Map<String, dynamic> json) {
if (json['result'] is List) {
final personsFromJson = json['result'] as List;
return PersonList(listOfPerson: [
...personsFromJson
.cast<Map<String, Object>>()
.map((i) => Person.fromJson(i))
]);
} else {
final personFromJson = json['result'] as Map<String, Object>;
return PersonList(listOfPerson: [Person.fromJson(personFromJson)]);
}
}
}
class Person {
String name;
int age;
Person({this.name, this.age});
factory Person.fromJson(Map<String, dynamic> json) {
return Person(name: json['name'] as String, age: json['age'] as int);
}
#override
String toString() => '$name (age: $age)';
}