flutter/cloud firestore :如何从文档中只获取一个数据？

import 'package:cloud_firestore/cloud_firestore.dart';

void fetchData() async {
  // 初始化 Firestore 实例
  FirebaseFirestore firestore = FirebaseFirestore.instance;

  // 指定集合和文档路径
  String collectionPath = 'yourCollection';
  String documentPath = 'yourDocument';

  // 获取文档引用
  DocumentReference docRef = firestore.collection(collectionPath).doc(documentPath);

  // 获取文档数据
  DocumentSnapshot documentSnapshot = await docRef.get();

  if (documentSnapshot.exists()) {
    // 获取特定字段的数据
    String data = documentSnapshot.data()['yourField'];
    print('Data: $data');
  } else {
    print('Document does not exist');
  }
}

if (documentSnapshot.exists()) {
  String data = documentSnapshot.data()['yourField'];
  print('Data: $data');
} else {
  print('Document does not exist');
}

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if request.auth != null;
    }
  }
}