I am facing an issue when data is fetched from the api and is not mapped into the model and the following error is thrown I have also posted the BodyModel class which contains the fromJson function:

Future<BodyModel> fetchJson(http.Client client, String? id) async {
  final response = await client.get(
    Uri.parse(uri2),
  );
  if (response.statusCode == 200) {
    String jsonData = response.body;

    print(response.body);
    //print(jsonEncode(response.body));

    BodyModel alpha = responseJSON(jsonData);
    //print(alpha.toSet());
    //bravo = alpha;
    return alpha;
  } else {
    throw Exception('We were not able to successfully download the json data.');
  }
}

BodyModel responseJSON(String response) {
  final parse = jsonDecode(response);

  print(parse.toString());

  final resp = parse<BodyModel>((json) => BodyModel.fromJson(json));
  print(resp);
  return resp;
}

import 'package:flutter/material.dart';

class BodyModel {
  String body;
  String title;

  BodyModel({
    required this.body,
    required this.title,
  });

  factory BodyModel.fromJson(Map<String, dynamic> jsonData) {
    return BodyModel(
      body: jsonData['body'].toString(),
      title: jsonData['title'].toString(),
    );
  }
}

CodePudding user response：

You are calling parse<BodyModel>(...). It's not clear what you think that's supposed to do, but parse is a variable containing a Map<String, dynamic>, not a generic function. It has type dynamic, so you won't get any warnings when misusing it. Consider declaring parse as

Map<String, dynamic> parse = jsonDecode(response);

so it has the correct type.

From the return type of responseJSON, my guess is that you want to do:

final resp = BodyModel.fromJson(parse);