flutter building listview with response from restapi - flutter

Question

typical json response:
{"data":[{"id":1,"partnerTypeId":1,"active":true,"name":"Covin - AINO UG","shortname":"Covin","firstname":null,"lastname":null,"addressId":1,"phoneId":null,"countryId":"in","email":"support#covin.in","web":"www.covin.in","infos":{},"note":null,"createdAt":"2021-03-06 23:30:30","updatedAt":"2021-03-06 23:30:30","updatedBy":null},{"id":41,"partnerTypeId":100,"active":true,"name":"Tester IND","shortname":"T.","firstname":null,"lastname":null,"addressId":null,"phoneId":null,"countryId":"IN","email":"email#tester","web":null,"infos":{},"note":null,"createdAt":"2021-03-06 23:32:02","updatedAt":"2021-03-07 01:25:06","updatedBy":null},{"id":42,"partnerTypeId":100,"active":true,"name":"MIT Charl","shortname":"KITA Ch.","firstname":null,"lastname":null,"addressId":null,"phoneId":null,"countryId":"IN","email":"kisa1#kol","web":null,"infos":{},"note":null,"createdAt":"2021-03-06 23:32:42","updatedAt":"2021-03-07 01:25:08","updatedBy":null}]}
Generated podo class:
filename- partnerList.dart
// To parse this JSON data, do
//
// final partnerList = partnerListFromMap(jsonString);
import 'dart:convert';
PartnerList partnerListFromMap(String str) => PartnerList.fromMap(json.decode(str));
String partnerListToMap(PartnerList data) => json.encode(data.toMap());
class PartnerList {
PartnerList({
this.data,
});
List<Datum> data;
factory PartnerList.fromMap(Map<String, dynamic> json) => PartnerList(
data: List<Datum>.from(json["data"].map((x) => Datum.fromMap(x))),
);
Map<String, dynamic> toMap() => {
"data": List<dynamic>.from(data.map((x) => x.toMap())),
};
}
class Datum {
Datum({
this.id,
this.partnerTypeId,
this.active,
this.name,
this.shortname,
this.firstname,
this.lastname,
this.addressId,
this.phoneId,
this.countryId,
this.email,
this.web,
this.infos,
this.note,
this.createdAt,
this.updatedAt,
this.updatedBy,
});
int id;
int partnerTypeId;
bool active;
String name;
String shortname;
dynamic firstname;
dynamic lastname;
int addressId;
dynamic phoneId;
String countryId;
String email;
String web;
Infos infos;
dynamic note;
DateTime createdAt;
DateTime updatedAt;
dynamic updatedBy;
factory Datum.fromMap(Map<String, dynamic> json) => Datum(
id: json["id"],
partnerTypeId: json["partnerTypeId"],
active: json["active"],
name: json["name"],
shortname: json["shortname"],
firstname: json["firstname"],
lastname: json["lastname"],
addressId: json["addressId"] == null ? null : json["addressId"],
phoneId: json["phoneId"],
countryId: json["countryId"],
email: json["email"],
web: json["web"] == null ? null : json["web"],
infos: Infos.fromMap(json["infos"]),
note: json["note"],
createdAt: DateTime.parse(json["createdAt"]),
updatedAt: DateTime.parse(json["updatedAt"]),
updatedBy: json["updatedBy"],
);
Map<String, dynamic> toMap() => {
"id": id,
"partnerTypeId": partnerTypeId,
"active": active,
"name": name,
"shortname": shortname,
"firstname": firstname,
"lastname": lastname,
"addressId": addressId == null ? null : addressId,
"phoneId": phoneId,
"countryId": countryId,
"email": email,
"web": web == null ? null : web,
"infos": infos.toMap(),
"note": note,
"createdAt": createdAt.toIso8601String(),
"updatedAt": updatedAt.toIso8601String(),
"updatedBy": updatedBy,
};
}
class Infos {
Infos();
factory Infos.fromMap(Map<String, dynamic> json) => Infos(
);
Map<String, dynamic> toMap() => {
};
}
related fetch class: file name - partner.api.dart
import 'partnerList.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:http/http.dart' as http;
Future<List<PartnerList>> fetchPartner() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
final userid = prefs.getString('user_id');
final token = prefs.getString('token');
Map<String, String> requestHeaders = {
'Accept': 'application/json',
// "Content-Type": "application/x-www-form-urlencoded",
'Authorization': 'Bearer $token',
};
final response = await http.get("https://api.covin.in/partners/",
headers: requestHeaders);
if (response.statusCode == 200) {
// If the server did return a 200 OK response,
// then parse the JSON.
print(response.body);
return partnerListFromMap(response.body);
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
throw Exception('Failed to load PartnerList');
}
}
Now the first error I am getting:
A value of type 'PartnerList' can't be returned from the function 'fetchPartner' because it has a return type of 'Future<List<PartnerList>>'.dartreturn_of_invalid_type
how I can fix this?
update: I have modified the function partnerListfromMap like below:
List<PartnerList> partnerListFromMap(String str) => List<PartnerList>.from(json.decode(str));
String partnerListToMap(PartnerList data) => json.encode(data.toMap());
but I am getting another error now:
Exception has occurred. _TypeError (type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>')

Answer 1

You can copy paste run full code below
Your json string is PartnerList not List<PartnerList>
You can use Future<PartnerList> and use return Future.value
code snippet
Future<PartnerList> fetchPartner() async {
...
return Future.value(partnerListFromMap(response.body));
working demo
full code
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
PartnerList partnerListFromMap(String str) =>
PartnerList.fromMap(json.decode(str));
String partnerListToMap(PartnerList data) => json.encode(data.toMap());
class PartnerList {
PartnerList({
this.data,
});
List<Datum> data;
factory PartnerList.fromMap(Map<String, dynamic> json) => PartnerList(
data: List<Datum>.from(json["data"].map((x) => Datum.fromMap(x))),
);
Map<String, dynamic> toMap() => {
"data": List<dynamic>.from(data.map((x) => x.toMap())),
};
}
class Datum {
Datum({
this.id,
this.partnerTypeId,
this.active,
this.name,
this.shortname,
this.firstname,
this.lastname,
this.addressId,
this.phoneId,
this.countryId,
this.email,
this.web,
this.infos,
this.note,
this.createdAt,
this.updatedAt,
this.updatedBy,
});
int id;
int partnerTypeId;
bool active;
String name;
String shortname;
dynamic firstname;
dynamic lastname;
int addressId;
dynamic phoneId;
String countryId;
String email;
String web;
Infos infos;
dynamic note;
DateTime createdAt;
DateTime updatedAt;
dynamic updatedBy;
factory Datum.fromMap(Map<String, dynamic> json) => Datum(
id: json["id"],
partnerTypeId: json["partnerTypeId"],
active: json["active"],
name: json["name"],
shortname: json["shortname"],
firstname: json["firstname"],
lastname: json["lastname"],
addressId: json["addressId"] == null ? null : json["addressId"],
phoneId: json["phoneId"],
countryId: json["countryId"],
email: json["email"],
web: json["web"] == null ? null : json["web"],
infos: Infos.fromMap(json["infos"]),
note: json["note"],
createdAt: DateTime.parse(json["createdAt"]),
updatedAt: DateTime.parse(json["updatedAt"]),
updatedBy: json["updatedBy"],
);
Map<String, dynamic> toMap() => {
"id": id,
"partnerTypeId": partnerTypeId,
"active": active,
"name": name,
"shortname": shortname,
"firstname": firstname,
"lastname": lastname,
"addressId": addressId == null ? null : addressId,
"phoneId": phoneId,
"countryId": countryId,
"email": email,
"web": web == null ? null : web,
"infos": infos.toMap(),
"note": note,
"createdAt": createdAt.toIso8601String(),
"updatedAt": updatedAt.toIso8601String(),
"updatedBy": updatedBy,
};
}
class Infos {
Infos();
factory Infos.fromMap(Map<String, dynamic> json) => Infos();
Map<String, dynamic> toMap() => {};
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<PartnerList> _future;
Future<PartnerList> fetchPartner() async {
String jsonString = '''
{"data":[{"id":1,"partnerTypeId":1,"active":true,"name":"Covin - AINO UG","shortname":"Covin","firstname":null,"lastname":null,"addressId":1,"phoneId":null,"countryId":"in","email":"support#covin.in","web":"www.covin.in","infos":{},"note":null,"createdAt":"2021-03-06 23:30:30","updatedAt":"2021-03-06 23:30:30","updatedBy":null},{"id":41,"partnerTypeId":100,"active":true,"name":"Tester IND","shortname":"T.","firstname":null,"lastname":null,"addressId":null,"phoneId":null,"countryId":"IN","email":"email#tester","web":null,"infos":{},"note":null,"createdAt":"2021-03-06 23:32:02","updatedAt":"2021-03-07 01:25:06","updatedBy":null},{"id":42,"partnerTypeId":100,"active":true,"name":"MIT Charl","shortname":"KITA Ch.","firstname":null,"lastname":null,"addressId":null,"phoneId":null,"countryId":"IN","email":"kisa1#kol","web":null,"infos":{},"note":null,"createdAt":"2021-03-06 23:32:42","updatedAt":"2021-03-07 01:25:08","updatedBy":null}]}
''';
final response = http.Response(jsonString, 200);
if (response.statusCode == 200) {
// If the server did return a 200 OK response,
// then parse the JSON.
print(response.body);
return Future.value(partnerListFromMap(response.body));
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
throw Exception('Failed to load PartnerList');
}
}
#override
void initState() {
_future = fetchPartner();
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<PartnerList> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('none');
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return ListView.builder(
itemCount: snapshot.data.data.length,
itemBuilder: (context, index) {
return Card(
elevation: 6.0,
child: Padding(
padding: const EdgeInsets.only(
top: 6.0,
bottom: 6.0,
left: 8.0,
right: 8.0),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(snapshot.data.data[index].id
.toString()),
Spacer(),
Text(
snapshot.data.data[index].name,
),
],
),
));
});
}
}
}));
}
}

Answer 2

Try this:
// this is correct. I think you generated this using app.quicktype.io ? Then it's correct.
PartnerList partnerListFromMap(String str) => PartnerList.fromMap(json.decode(str));
// you want the list of Datum.
Future<List<Datum>> fetchPartner() async {
// other codes here ...
return partnerListFromMap(response.body).data;
// other codes here ...
}