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'

CodePudding user response：

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;
    }
  }
}

CodePudding user response：

 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;
}

}