​
Code Explained - Question Text :
import './question.dart';

class Quiz {
  List<Question> _questions;
  int _currentQuestionIndex = -1;
  int _score = 0;


  Quiz(this._questions) {
    _questions.shuffle();
  }

  List<Question> get questions => _questions;
  int get length => _questions.length;
  int get questionNumber => _currentQuestionIndex+1;
  int get score => _score;

  Question get nextQuestion {
    _currentQuestionIndex++;
    if (_currentQuestionIndex >= length) return null;
    return _questions[_currentQuestionIndex];
  }

  void answer(bool isCorrect) {
    if (isCorrect){
      _score++;
    }
  }


}

---