Flutter: Join specific field of JSON file together to become a list itself - json

Question

I have a json file with a list of different types of data.
I wanted to join the "name" field of all attractions of each city together as a list.
The expected result after joining, for example for Longo city will be like this:
Attraction1
Attraction2
The data in JSON file is structured like this:
{
"city": "London",
"attractions": [
{
"name": "Attraction1",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction2",
"localrank": 4,
"intrank": 5
}
]
},
{
"city": "Hong Kong",
"attractions": [
{
"name": "Attraction3",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction4",
"localrank": 4,
"intrank": 5
}
]
},
{
"city": "Cario",
"attractions": [
{
"name": "Attraction5",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction6",
"localrank": 4,
"intrank": 5
}
]
}
]
I used the following code, but I get an error :
cities.attractions.name.join("\n")
Json model class is this:
List<Cities> citiesFromJson(String str) =>
List<Cities>.from(json.decode(str).map((x) => Cities.fromJson(x)));
String citiesToJson(List<Cities> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Cities {
Cities({
this.city,
this.attractions,
});
String city;
List<Attraction> attractions;
factory Cities.fromRawJson(String str) => Cities.fromJson(json.decode(str));
String toRawJson() => json.encode(toJson());
factory Cities.fromJson(Map<String, dynamic> json) => Cities(
city: json["city"],
attractions: List<Attraction>.from(
json["attractions"].map((x) => Attraction.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"city": city,
"attractions": List<dynamic>.from(attractions.map((x) => x.toJson())),
};
}
class Attraction {
Attraction({
this.name,
this.localrank,
this.intrank,
});
String name;
int localrank;
int intrank;
factory Attraction.fromRawJson(String str) =>
Attraction.fromJson(json.decode(str));
String toRawJson() => json.encode(toJson());
factory Attraction.fromJson(Map<String, dynamic> json) => Attraction(
name: json["name"],
localrank: json["localrank"],
intrank: json["intrank"],
);
Map<String, dynamic> toJson() => {
"name": name,
"localrank": localrank,
"intrank": intrank,
};
}
And this also calling json file:
Future<String> fetchData() async {
String data =
await DefaultAssetBundle.of(context).loadString("assets/data.json");
final jsonResult = json.decode(data);
print('$jsonResult oop');
this.setState(() {
jsonResult.forEach(
(element) => Globals.citylist.add(new Cities.fromJson(element)));
});
return "Success!";
}

Answer 1

Something like that should work:
import 'dart:convert';
var data = """ [{
"city": "London",
"attractions": [
{
"name": "Attraction1",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction2",
"localrank": 4,
"intrank": 5
}
]
},
{
"city": "Hong Kong",
"attractions": [
{
"name": "Attraction3",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction4",
"localrank": 4,
"intrank": 5
}
]
},
{
"city": "Cario",
"attractions": [
{
"name": "Attraction5",
"localrank": 10,
"intrank": 4
},
{
"name": "Attraction6",
"localrank": 4,
"intrank": 5
}
]
}
] """;
List<Cities> citiesFromJson(String str) =>
List<Cities>.from(json.decode(str).map((x) => Cities.fromJson(x)));
String citiesToJson(List<Cities> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class Cities {
Cities({
this.city,
this.attractions,
});
String city;
List<Attraction> attractions;
factory Cities.fromRawJson(String str) => Cities.fromJson(json.decode(str));
String toRawJson() => json.encode(toJson());
factory Cities.fromJson(Map<String, dynamic> json) => Cities(
city: json["city"],
attractions: List<Attraction>.from(
json["attractions"].map((x) => Attraction.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"city": city,
"attractions": List<dynamic>.from(attractions.map((x) => x.toJson())),
};
}
class Attraction {
Attraction({
this.name,
this.localrank,
this.intrank,
});
String name;
int localrank;
int intrank;
factory Attraction.fromRawJson(String str) =>
Attraction.fromJson(json.decode(str));
String toRawJson() => json.encode(toJson());
factory Attraction.fromJson(Map<String, dynamic> json) => Attraction(
name: json["name"],
localrank: json["localrank"],
intrank: json["intrank"],
);
Map<String, dynamic> toJson() => {
"name": name,
"localrank": localrank,
"intrank": intrank,
};
}
class Globals {
static List<Cities> citylist = [];
}
Future<String> fetchData() async {
// String data =
// await DefaultAssetBundle.of(context).loadString("assets/data.json");
final jsonResult = json.decode(data);
print('$jsonResult oop');
// this.setState(() {
jsonResult.forEach(
(element) => Globals.citylist.add(new Cities.fromJson(element)));
// });
var result = getAttractionsByCity('London');
print(result.join('\n'));
return "Success!";
}
List<String> getAttractionsByCity(String value) {
var result = <String>[];
for (final city in Globals.citylist) {
if (city.city == value) {
final attractions = city.attractions;
for (final attraction in attractions) {
result.add(attraction.name);
}
}
}
return result;
}
void main() async {
await fetchData();
}
It's a working example. You can copy and paste this code to HTTP://dartpad.dev and run it to see the result.