Flutter-Firestore "The argument type 'Map<String, dynamic> Function()' can't be assigned to the parameter type 'Map<String, dynamic>"

Question

我尝试在 firebase firestore 中查看我的数据。但是这个错误是我的 firestore_service.dart file.Can 你帮我解决这个错误。

"参数类型 'Map<String, dynamic> Function()' 无法分配给参数类型 'Map"

这是我的firestore_service.dart

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:esrimarket/note.dart';
import 'package:flutter/foundation.dart';

class FirestoreService {
  static final FirestoreService _firestoreService =
      FirestoreService._internal();
  Firestore _db = Firestore.instance;

  FirestoreService._internal();

  factory FirestoreService() {
    return _firestoreService;
  }

  getNotes(){
    return _db
    .collection('notes')
    .snapshots()
    .map((snapshot)=>snapshot.documents.map((doc)=>Note.fromMap(doc.data, doc.documentID)));
  }
}

这是我的 note.dart 文件

class Note{
  final String name;
  final String price;
  final String quantity;
  final String id;

  Note({this.name, this.price, this.quantity, this.id});

  Note.fromMap(Map<String,dynamic> data, String id):
    name=data["name"],
    price=data["price"],
    quantity=data["quantity"],
    id=id;
}

Answer 1

您在成员 data 后缺少括号，因为它是一个函数：

Note.fromMap(doc.data(), doc.documentID)

                     ^^