Flutter Firestore 通过流函数从特定文档中读取特定字段

Question

基本上我正在努力在我的database.dart 中创建一个函数，我可以在其中调用此函数来显示特定文档中的特定字段。

例如，我想使用Database.readUserProfileData('Profile', 'surname') 将字符串/alt 显示到小部件。

static Future<QuerySnapshot> readUserProfileData({
    required String docId,
    required String field,
  }) async {
    var ref = _mainCollection.get().then((querySnapshot) {
      querySnapshot.docs.forEach((result) {
        Object? data = result.data();
        print(data);
      });
    });
  }

这是我的database.dart

（请忽略UpdateItem 功能，因为我没有正确配置它，因为我从模板复制了它，或者可能为我更新它，哈哈抱歉；））

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';

final FirebaseFirestore _firestore = FirebaseFirestore.instance;

/* ------------------ Database Reference - Main Collection ------------------ */
final CollectionReference _mainCollection = _firestore.collection('_TestFB');

class Database {
  static String? userUid;

  /* -------------------------- Create User Database -------------------------- */
  static Future<void> createUserDataFile({
    required String uid,
    required String surname,
    required int mobile,
  }) async {
    DocumentReference documentReferencer =
        _mainCollection.doc('UserData').collection(uid).doc('Profile');

    Map<String, dynamic> data = <String, dynamic>{
      "surname": surname,
      "mobile": mobile,
    };

    _mainCollection
        .doc('UserData')
        .collection(uid)
        .limit(1)
        .get()
        .then((snapshot) async {
      if (snapshot.size == 1) {
        print("**User Profile Exists");
      } else {
        await documentReferencer
            .set(data)
            .whenComplete(() => print("**New Profile Created for - " + uid))
            .catchError((e) => print(e));
      }
    });
  }

  /* ------------------------- Read User Profile Data ------------------------- */
  static Future<QuerySnapshot> readUserProfileData({
    required String docId,
    required String field,
  }) async {
    var ref = _mainCollection.get().then((querySnapshot) {
      querySnapshot.docs.forEach((result) {
        Object? data = result.data();
        print(data);
      });
    });
  }

提前致谢

Answer 1

如果您已经有了文档 ID，那么只需执行以下操作：

static Future<DocumentSnapshot> readUserProfileData({
    required String docId,
    required String field,
  }) async {
    var ref = _mainCollection.doc(docId).get().then((snapshot) {
        print(snapshot);
        print(snapshot.data()[field]);
    });
  }

您不需要使用forEach，因为您只检索一个文档，而get() 将有一个返回类型Future<DocumentSnapshot>