I am trying to get data from API but having error - flutter

Question

This is my model class and I am trying to get all the data but getting error and don't know why.
HomePageModel homePageModelFromJson(String str) => HomePageModel.fromJson(json.decode(str));
String homePageModelToJson(HomePageModel data) => json.encode(data.toJson());
class HomePageModel with ChangeNotifier {
HomePageModel({
this.data,
});
List<Datum>? data;
factory HomePageModel.fromJson(Map<String, dynamic> json) => HomePageModel(
data: List<Datum>.from(json["data"]!.map((x) => Datum.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"data": List<dynamic>.from(data!.map((x) => x.toJson())),
};
}
class Datum {
Datum({
this.schoolid,
this.name,
this.logo,
this.address,
this.contact,
this.principalname,
this.principalcontact,
this.slogan,
this.webAddress,
this.description,
this.email,
this.pan,
this.establishedYear,
});
String? schoolid;
String? name;
String? logo;
String? address;
String? contact;
String? principalname;
String? principalcontact;
String? slogan;
String? webAddress;
String? description;
String? email;
String? pan;
int? establishedYear;
factory Datum.fromJson(Map<String, dynamic> json) => Datum(
schoolid: json["schoolid"],
name: json["name"],
logo: json["logo"],
address: json["address"],
contact: json["contact"],
principalname: json["principalname"],
principalcontact: json["principalcontact"],
slogan: json["slogan"],
webAddress: json["web_address"] == null ? null : json["web_address"],
description: json["description"] == null ? null : json["description"],
email: json["email"],
pan: json["pan"],
establishedYear: json["established_year"],
);
Map<String, dynamic> toJson() => {
"schoolid": schoolid,
"name": name,
"logo": logo,
"address": address,
"contact": contact,
"principalname": principalname,
"principalcontact": principalcontact,
"slogan": slogan,
"web_address": webAddress == null ? null : webAddress,
"description": description == null ? null : description,
"email": email,
"pan": pan,
"established_year": establishedYear,
};
}
This is how I am trying to fetch data:
class HomePageModels with ChangeNotifier{
List<HomePageModel> _hItem = [];
List<HomePageModel> get hItem{
return [..._hItem];
}
Future<void> getHomeData(BuildContext context) async{
const url = "https://shikshyasoftware.com.np/CoreApplicationandAPIService-4617993073/api/school";
try{
// EasyLoading.show(status: 'Loading...');
final response = await http.get(Uri.parse(url));
final extractedData = json.decode(response.body);
List<HomePageModel> loadedHomeData = [];
if(extractedData == null){
return;
}
if(response.statusCode == 200){
print(extractedData);
}
extractedData.forEach((element){
loadedHomeData.add(HomePageModel.fromJson(element));
});
_hItem = loadedHomeData;
// EasyLoading.showSuccess("data fetched sucessfull");
notifyListeners();
}catch(e){
rethrow;
}
}
}
But I am getting error:
[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: type '(dynamic) => Null' is not a subtype of type '(String, dynamic) => void' of 'f'

Answer 1

The problem is the way you are trying to parse the data, you don't need to loop over every element to parse it, in your model just make it return a list type like this,
class HomePageModel with ChangeNotifier {
List<Datum>? data;
HomePageModel({this.data});
HomePageModel.fromJson(Map<String, dynamic> json) {
if (json['data'] != null) {
data = <Datum>[];
json['data'].forEach((v) {
data!.add(new Datum.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.data != null) {
data['data'] = this.data!.map((v) => v.toJson()).toList();
}
return data;
}
}
class Datum {
Datum({
this.schoolid,
this.name,
this.logo,
this.address,
this.contact,
this.principalname,
this.principalcontact,
this.slogan,
this.webAddress,
this.description,
this.email,
this.pan,
this.establishedYear,
});
String? schoolid;
String? name;
String? logo;
String? address;
String? contact;
String? principalname;
String? principalcontact;
String? slogan;
String? webAddress;
String? description;
String? email;
String? pan;
int? establishedYear;
Datum.fromJson(Map<String, dynamic> json) {
schoolid = json["schoolid"];
name = json["name"];
logo = json["logo"];
address = json["address"];
contact = json["contact"];
principalname = json["principalname"];
principalcontact = json["principalcontact"];
slogan = json["slogan"];
webAddress = json["web_address"];
description = json["description"];
email = json["email"];
pan = json["pan"];
establishedYear = json["established_year"];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['schoolid'] = this.schoolid;
data['name'] = this.name;
data['logo'] = this.logo;
data['address'] = this.address;
data['contact'] = this.contact;
data['principalname'] = this.principalname;
data['principalcontact'] = this.principalcontact;
data['slogan'] = this.slogan;
data['web_address'] = this.webAddress;
data['description'] = this.description;
data['email'] = this.email;
data['pan'] = this.pan;
data['established_year'] = this.establishedYear;
return data;
}
}
and in your view model you can just parse the extracted data from response.body like this,
class HomePageModels with ChangeNotifier {
HomePageModel? _hItem;
HomePageModel get hItem {
return _hItem!;
}
Future<void> getHomeData(BuildContext context) async {
const url =
"https://shikshyasoftware.com.np/CoreApplicationandAPIService-
4617993073/api/school";
try {
// EasyLoading.show(status: 'Loading...');
final response = await http.get(Uri.parse(url));
final extractedData = json.decode(response.body);
if (extractedData == null) {
return;
}
if (response.statusCode == 200) {
print(extractedData);
}
HomePageModel loadedHomeData =
HomePageModel.fromJson(extractedData);
_hItem = loadedHomeData;
// EasyLoading.showSuccess("data fetched sucessfull");
notifyListeners();
} catch (e) {
rethrow;
}
}
}

Answer 2

getHomeData(BuildContext context) async {
const url =
"https://shikshyasoftware.com.np/CoreApplicationandAPIService-4617993073/api/school";
try {
// EasyLoading.show(status: 'Loading...');
final response = await http.get(Uri.parse(url));
if (response.statusCode == 200) {
final extractedData = json.decode(response.body);
List loadedHomeData = extractedData;
_hItem = loadedHomeData.map((e) => HomePageModel.fromJson(e)).toList();
}
notifyListeners();
return _hItem;
} catch (e) {
rethrow;
}
}