Flutter | 如何從 Firestore 獲取對象列表？

Question

這是我的問題 Object：

class Question {
  String text;
  String correctAnswer;
  bool answer;

  Question(String q, bool a, String ca) {
    text = q;
    answer = a;
    correctAnswer = ca;
  }
}

我想從 Firestore 獲取問題列表，如下所示：

List<Question> questionBank = [];

Firestore看起來像這樣：

我怎樣才能做到這一點？

Answer 1

你可以像這樣從firestore獲取數據

void _onPressed() {
  firestoreInstance.collection("Questiions").get().then((querySnapshot) {
    querySnapshot.docs.forEach((result) {
      print(result.data());
    });
  });
}

有關更多詳細信息，您可以參考此https://medium.com/firebase-tips-tricks/how-to-use-cloud-firestore-in-flutter-9ea80593ca40

Answer 2

從 Cloud Firestore 檢索問題並轉換為列表：

  Future<List<Question>> fetchQuestions(String userId) async {
    final questions = new List<Question>();
    final doc = await FirebaseFirestore.instance.collection('Questions').doc(userId).get();
    final questionsTmp = doc.data().questions;
    questionsTmp.forEach((questionTmp) {
      questions.add(Question.fromMap(questionTmp));
    });
    return questions;
  }

在問題 class 中添加 fromMap 方法：

class Question {
  String text;
  String correctAnswer;
  bool answer;

  Question(String q, bool a, String ca) {
    text = q;
    answer = a;
    correctAnswer = ca;
  }

  static Question fromMap(Map<String, dynamic> map) {
    return Question(
      map['text'],
      map['answer'],
      map['correctAnswer'].ToString() == 'true'
    );
  }
}