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Flutter Mobile Development · 课时

Cloud Firestore 数据库

使用 Cloud Firestore 这一 NoSQL 文档数据库，在所有已连接客户端之间实时存储和同步数据。

Cloud Firestore 数据库 是 CoddyKit 上的免费 Flutter Mobile Development 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Flutter Mobile Development 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Flutter Mobile Development 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

What is Cloud Firestore?

Welcome to Cloud Firestore! It's a flexible, scalable NoSQL document database for mobile, web, and server development from Firebase.

It keeps your data in sync across client apps in real-time and offers offline support, making it great for responsive apps.

How Data is Organized

Firestore stores data in documents, which are like JSON objects. Documents are organized into collections, which are containers for documents.

  • Collections: Groups of documents.
  • Documents: Key-value pairs (fields) that can contain subcollections.
  • Fields: The actual data points within a document.

Firestore vs. Realtime Database

Firebase offers two databases: Firestore and Realtime Database. Firestore is generally preferred for new apps due to its more intuitive data model, powerful querying, and better scalability.

Think of Firestore as a modern upgrade, offering better structure and query capabilities for complex data.

Accessing Firestore in Flutter

To interact with Firestore, first ensure you've initialized Firebase (from Lesson 1). Then, get an instance of FirebaseFirestore:

You'll need to add the cloud_firestore package to your pubspec.yaml.

import 'package:cloud_firestore/cloud_firestore.dart';
// Ensure Firebase is initialized in your main() or similar
// For example: await Firebase.initializeApp();

void main() {
  FirebaseFirestore db = FirebaseFirestore.instance;
  print("Firestore instance obtained!");
  // You would typically use this 'db' instance
  // within your Flutter widgets.
}

Storing New Documents

You can add data to Firestore using set() or add(). set() lets you specify the document ID, while add() auto-generates one.

Let's add a new user to a 'users' collection:

import 'package:cloud_firestore/cloud_firestore.dart';
// Assume Firebase.initializeApp() is done.

void main() async {
  FirebaseFirestore db = FirebaseFirestore.instance;

  // Using .add() - Firestore generates a document ID
  DocumentReference docRef = await db.collection("users").add({
    "name": "Alice",
    "email": "alice@example.com",
    "age": 30,
    "isActive": true
  });
  print("Document added with ID: ${docRef.id}");

  // Using .set() - you provide the document ID
  await db.collection("cities").doc("LA").set({
    "name": "Los Angeles",
    "state": "CA",
    "country": "USA"
  });
  print("City 'LA' added.");
}

Fetching Data Once

To read a single document, you reference its collection and ID, then call get().

This fetches the data once. We'll look at real-time updates next.

import 'package:cloud_firestore/cloud_firestore.dart';
// Assume Firebase.initializeApp() is done.

void main() async {
  FirebaseFirestore db = FirebaseFirestore.instance;

  // Replace 'some_doc_id' with an actual ID from your Firestore
  DocumentSnapshot doc = await db.collection("users").doc("some_doc_id").get();

  if (doc.exists) {
    print("Document data: ${doc.data()}");
    print("User name: ${doc.get('name')}");
  } else {
    print("No such document!");
  }
}

Modifying Existing Documents

Use the update() method on a document reference to change specific fields without overwriting the entire document.

This is useful for making small adjustments to existing records.

import 'package:cloud_firestore/cloud_firestore.dart';
// Assume Firebase.initializeApp() is done.

void main() async {
  FirebaseFirestore db = FirebaseFirestore.instance;

  // Replace 'some_doc_id' with an actual ID
  String docIdToUpdate = "some_doc_id";

  await db.collection("users").doc(docIdToUpdate).update({
    "age": 31,
    "city": "New York" // Add a new field
  });
  print("Document updated successfully!");

  // You can also update nested fields using dot notation
  // await db.collection("users").doc(docIdToUpdate).update({
  //   "address.street": "Main St"
  // });
}

Removing Documents and Fields

You can delete an entire document or just specific fields within a document.

  • Use delete() on a document reference to remove the whole document.
  • Use FieldValue.delete() in an update() call to remove a specific field.
import 'package:cloud_firestore/cloud_firestore.dart';
// Assume Firebase.initializeApp() is done.

void main() async {
  FirebaseFirestore db = FirebaseFirestore.instance;

  // Replace with an actual document ID you wish to delete
  String docIdToDelete = "some_other_doc_id";

  // Delete a specific field from a document
  await db.collection("users").doc("some_doc_id").update({
    "isActive": FieldValue.delete()
  });
  print("Field 'isActive' deleted from document 'some_doc_id'.");

  // Delete an entire document
  await db.collection("users").doc(docIdToDelete).delete();
  print("Document '${docIdToDelete}' deleted.");
}

Real-time Data Updates

One of Firestore's most powerful features is real-time data synchronization. Use snapshots() to listen for changes to a document or collection.

Your app will automatically receive updates whenever the data changes in the database.

import 'package:cloud_firestore/cloud_firestore.dart';
// Assume Firebase.initializeApp() is done.

void main() {
  FirebaseFirestore db = FirebaseFirestore.instance;

  // Listen to a single document
  db.collection("users").doc("some_doc_id").snapshots().listen((snapshot) {
    if (snapshot.exists) {
      print("Real-time update for doc: ${snapshot.data()}");
    } else {
      print("Document no longer exists.");
    }
  });

  // Listen to a whole collection
  db.collection("users").snapshots().listen((snapshot) {
    print("Real-time update for collection. Total docs: ${snapshot.docs.length}");
    for (var doc in snapshot.docs) {
      print("  - ${doc.id}: ${doc.data()['name']}");
    }
  });

  print("Listeners set up. App will now receive real-time updates.");
  // In a real Flutter app, this would be part of a StatefulWidget's initState
  // and listeners would be cancelled in dispose().
}

Advanced Data Queries

Firestore allows powerful queries to filter and order your data. You can chain multiple where() clauses and orderBy() calls.

  • where('field', isEqualTo: value)
  • orderBy('field', descending: true)
  • limit(count)

Remember, complex queries might require creating indexes in the Firebase console.

Firestore Operations Check

Which of the following statements about Cloud Firestore operations are TRUE?

Firestore Summary

Great job! You've learned the fundamentals of Cloud Firestore, including its NoSQL structure, how to add, read, update, and delete data.

We also explored real-time listeners and basic querying. Firestore is a powerful tool for building dynamic, data-driven Flutter apps!

Next, we'll explore Firebase Cloud Storage for handling larger files like images and videos.

常见问题解答

「Cloud Firestore 数据库」课时是免费的吗？

是的 — 「Cloud Firestore 数据库」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Flutter Mobile Development 课程的其余内容，请升级到 CoddyKit PRO。 Flutter Mobile Development 课程共包含 4 节课。

「Cloud Firestore 数据库」这节课中我会学到什么？

使用 Cloud Firestore 这一 NoSQL 文档数据库，在所有已连接客户端之间实时存储和同步数据。 你通过在浏览器中直接运行的动手代码来练习 Flutter Mobile Development，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Flutter Mobile Development 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Flutter Mobile Development 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。

「Cloud Firestore 数据库」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Flutter Mobile Development 课中编写并运行代码吗？

能。每节 Flutter Mobile Development 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. Firebase 配置与身份验证
  2. Cloud Firestore 数据库
  3. 云存储与云函数
  4. Firebase 云消息传递与通知
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