错误：参数类型“对象？”不能分配给参数类型 'Map<dynamic, dynamic>'

Question

factory Book.fromMap(Map map) => Book(
      id: map['id'],
      bookName: map['bookName'],
      authorName: map['authorName'],
      publishedDate: map['publishedDate']);

Stream<List<DocumentSnapshot>> streamListDocument = _database
        .getBookListApi(booksRef)
        .map((querySnapshot) => querySnapshot.docs);

Stream<Iterable<Book>> streamListBook = streamListDocument.map((event) =>
        event.map((docSnap) => Book.fromMap(docSnap.data())));

        return streamListBook;

我的代码是这样的。 我还编辑了 Map 但问题并没有消失。

Answer 1

尝试Book.fromMap(docSnap.data() as Map<String,dynamic>) 看看它是否能解决您的问题。