During construction of a a prototype for a quiz app using Flutter and VS Code as the IDE, I got the following error:

type 'List<Map<String, Object>>' is not a subtype of type 'List<Map<String, int>>' in type cast

from my quiz.dart file which is

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

import './answer.dart';
import './question.dart';

class Quiz extends StatelessWidget {
  final Function? fun;
  final int? questionIndex;
  final List<Map<String, Object>>? array;

  Quiz({required this.fun, required this.questionIndex, required this.array});
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          (array)![questionIndex!]['questionText'] as String,
        ),
        ...((array)![questionIndex!]['answers'] as List<Map<String, int>>)
            .map((question) {
          return Answer((() => (fun!(question['score'])) as VoidCallback),
              (question['text'] as String));
        }).toList(),
        // ...[Text('hello'), Text('okay')],
      ],
    );
  }
}

Following is my main.dart file where one can find my plugin for array in the constructor of Quiz widget class.

import 'package:flutter/material.dart';

import './quiz.dart';
import './result.dart';
// void main() {
//   runApp(MyApp());
// }

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _MyAppState();
  }
}

class _MyAppState extends State<MyApp> {
  final _ques = const [
    {
      'questionText': 'What\'s your fav. color?',
      'answers': [
        {'text': 'Black', 'score': 10},
        {'text': 'Red', 'score': 5},
        {'text': 'Green', 'score': 3},
        {'text': 'White', 'score': 1},
      ]
    },
    {
      'questionText': 'What\'s your fav. animal?',
      'answers': [
        {'text': 'Cat', 'score': 5},
        {'text': 'Dog', 'score': 3},
        {'text': 'Snake', 'score': 4},
        {'text': 'Bird', 'score': 2}
      ]
    },
    {
      'questionText': 'Who\'s your fav. instructor?',
      'answers': [
        {'text': 'Max', 'score': 1},
        {'text': 'Max', 'score': 1},
        {'text': 'Max', 'score': 1}
      ]
    },
  ];

  var _questionIndex = 0;
  var _totalScore = 0;

  void _hola(int score) {
    _totalScore  = score;

    setState(() => _questionIndex = _questionIndex   1);
    print(_questionIndex);
    if (_questionIndex < _ques.length) {
      print('We have more questions!!');
    }
  }

  @override
  Widget build(BuildContext context) {
    // print('hpllll ${context}');

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Ayoo App Bar stuff'),
          backgroundColor: Colors.black,
        ),
        body: _questionIndex < _ques.length
            ? Quiz(questionIndex: _questionIndex, array: _ques, fun: _hola)
            : Result(_totalScore),
      ),
    );
  }
}

In fact, I get an error even when I use

final List<Map<String,List<Map<String,int>>>> _ques = const [
    {
      'questionText': 'What\'s your fav. color?',
      'answers': [
        {'text': 'Black', 'score': 10},
        {'text': 'Red', 'score': 5},
        {'text': 'Green', 'score': 3},
        {'text': 'White', 'score': 1},
      ]
    },
    {
      'questionText': 'What\'s your fav. animal?',
      'answers': [
        {'text': 'Cat', 'score': 5},
        {'text': 'Dog', 'score': 3},
        {'text': 'Snake', 'score': 4},
        {'text': 'Bird', 'score': 2}
      ]
    },
    {
      'questionText': 'Who\'s your fav. instructor?',
      'answers': [
        {'text': 'Max', 'score': 1},
        {'text': 'Max', 'score': 1},
        {'text': 'Max', 'score': 1}
      ]
    },
  ];

to explicitly define the datatype for _ques list. Following is a screenshot showing the error

Any help in regard to fixing/explaining this error is highly appreciated!

CodePudding user response：

Because of the type :

List<Map<String,List<Map<String,int>>>>

You created a list of map where the left Side are always String and the Right side must be always List of Map<String, int>. I suggest to use the following type instead :

List<Map<String, dynamic>>