从Firestore和Flutter中嵌套在数组中的地图中获取数据

{
  "users": {
    "userId1": {
      "friends": [
        {
          "friendId": "friendId1",
          "name": "Alice",
          "age": 25
        },
        {
          "friendId": "friendId2",
          "name": "Bob",
          "age": 30
        }
      ]
    }
  }
}

import 'package:cloud_firestore/cloud_firestore.dart';

void fetchUserFriends(String userId) async {
  try {
    QuerySnapshot querySnapshot = await FirebaseFirestore.instance
        .collection('users')
        .doc(userId)
        .get();

    if (querySnapshot.exists) {
      var friendsData = querySnapshot.data()?['friends'] as List?;
      if (friendsData != null) {
        for (var friend in friendsData) {
          print('Friend ID: ${friend['friendId']}');
          print('Name: ${friend['name']}');
          print('Age: ${friend['age']}');
        }
      }
    } else {
      print('User not found');
    }
  } catch (e) {
    print('Error fetching user friends: $e');
  }
}

var friendsData = querySnapshot.data()?['friends'] as List?;
if (friendsData != null) {
  for (var friend in friendsData) {
    if (friend is Map<String, dynamic>) {
      print('Friend ID: ${friend['friendId']}');
      print('Name: ${friend['name']}');
      print('Age: ${friend['age']}');
    }
  }
}

if (querySnapshot.exists) {
  var friendsData = querySnapshot.data()?['friends'] as List?;
  if (friendsData != null) {
    // Process friends data
  } else {
    print('No friends data found');
  }
} else {
  print('User not found');
}