error getting value, NoSuchMethodError : (function)

Question

what this mean error:

my goals is when i'm click the button, result will be display value control flow function, this my code:

data:

var question = const [
    {
      'questionHere': 'which ur hate friend as?',
      'answer': [
        {'name': 'Dendi', 'score': 0},
        {'name': 'Yogi', 'score': 10},
        {'name': 'Vali', 'score': 7},
        {'name': 'Odir', 'score': 10},
        {'name': 'Vega', 'score': 8},
      ],
    },
    {
      'questionHere': 'What is ur fav Smoke?',
      'answer': [
        {'name': 'Marlboro', 'score': 10},
        {'name': 'Sampurna', 'score': 7},
        {'name': 'Surya', 'score': 8},
        {'name': 'Surya Pro mild', 'score': 5},
      ],
    }
  ];

main.dart

import 'package:flutter/material.dart';
import 'package:trying/widget/quiz.dart';
import 'package:trying/widget/result.dart';

void main() => runApp(MaterialApp(
      home: HomePage(),
    ));

class HomePage extends StatefulWidget {
  HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  var _questionNumber = 0;
  var _totalScore = 0;
 

  void _questionInc(int score) {
    _totalScore += score;
    setState(() {
      _questionNumber++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _questionNumber < question.length
          ? Quiz(question, _questionInc, _questionNumber)
          : Result(_totalScore),
    );
  }
}

result.dart

import 'package:flutter/material.dart';

class Result extends StatelessWidget {
  final int resultScore;
  Result(this.resultScore);

this case about score will be display, but i still get error

  String get score {
    String resultText = '';
    if (resultScore <= 10) {
      resultText = 'bego';
    } else if (resultScore < 8) {
      resultText = 'a';
    } else {
      return resultText;
    }
    throw Exception();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(score),
    );
  }
}

this button widget

increment.dart

import 'package:flutter/material.dart';

class Inc extends StatelessWidget {
  final VoidCallback selectInc;
  final String answer;
  Inc(this.selectInc, this.answer);

  @override
  Widget build(BuildContext context) {
    return Container(
        margin: EdgeInsets.all(16),
        width: double.infinity,
        height: 20,
        child: ElevatedButton(
          onPressed: selectInc,
          child: Text(answer),
        ));
  }
}

Quis.dart

import 'package:flutter/material.dart';
import './question.dart';
import './increment.dart';

class Quiz extends StatelessWidget {
  final Function questionInc;
  final int questionIndex;
  final List<Map<String, Object>> questionData;

  Quiz(this.questionData, this.questionInc, this.questionIndex);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Question(questionData[questionIndex]['questionHere'] as String),
          ...(questionData[questionIndex]["answer"]
                  as List<Map<String, Object>>)
              .map((e) => Inc(questionInc(), e["name"] as String))
              .toList()
        ],
      ),
    );
  }
}

so how to fixed this problem, how to know even value has return?

Answer 1

In your class, Quiz. Make questionInc as VoidCallback and also when calling Inc pass it as reference.