Firebase Auth & Realtime Database Apps · 课时

将用户数据连接到身份验证

将已通过身份验证的用户 ID 与 Realtime Database 中对应的数据条目关联起来，以提供个性化内容

将用户数据连接到身份验证 是 CoddyKit 上的免费 Firebase Auth & Realtime Database Apps 课时。这是第 1 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 Firebase Auth & Realtime Database Apps 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Firebase Auth & Realtime Database Apps 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。

Link Auth & Database

Why connect user authentication with your database? It's crucial for building personalized and secure applications.

By linking, you can:

Store user-specific data like profiles or settings.
Control access to data based on who is logged in.
Create personalized experiences for each user.

Accessing the User's UID

Every authenticated user in Firebase has a unique User ID (UID). This ID is your key to linking their authentication status to their data.

You can get the current user's UID from the currentUser object after a user signs in.

<!-- Assume Firebase SDKs are loaded -->
<!-- and firebase.initializeApp() has been called -->

<script>
  // Listen for authentication state changes
  firebase.auth().onAuthStateChanged(user => {
    if (user) {
      const uid = user.uid;
      console.log("Current User UID:", uid);
      // Example: Display UID in a web element
      // document.getElementById('user-uid').innerText = uid;
    } else {
      console.log("No user signed in.");
    }
  });
</script>

UID as Your Database Key

Once you have the UID, you can use it as a unique identifier in your Firebase Realtime Database paths. This creates a secure and organized way to store user-specific data.

Think of it like a folder for each user, named after their UID:

/users/{UID}/profile
/users/{UID}/preferences

Storing First User Data

Let's store some basic profile information for a signed-in user. We'll use the user's UID to create a unique path in the database.

This example stores a username and email under /users/{uid}.

<!-- Assume Firebase SDKs loaded & initialized -->

<script>
  const user = firebase.auth().currentUser;

  if (user) {
    const uid = user.uid;
    const userRef = firebase.database().ref('users/' + uid);

    userRef.set({
      username: "JaneDoe",
      email: user.email, // Use auth email
      createdAt: firebase.database.ServerValue.TIMESTAMP
    })
    .then(() => {
      console.log("User data saved successfully!");
    })
    .catch(error => {
      console.error("Error saving user data:", error);
    });
  } else {
    console.log("No user signed in to save data for.");
  }
</script>

Your User Data Structure

After the previous code runs, your Realtime Database might look something like this:

{
  "users": {
    "YOUR_USER_UID_HERE": {
      "username": "JaneDoe",
      "email": "janedoe@example.com",
      "createdAt": 1678886400000
    }
  }
}

Each user gets their own top-level key under /users, making it easy to manage their data.

Reading User-Specific Data

To retrieve personalized content, you simply read from the path constructed with the current user's UID. This ensures they only see their own information.

Here's how to fetch the profile data we just stored:

<!-- Assume Firebase SDKs loaded & initialized -->

<script>
  const user = firebase.auth().currentUser;

  if (user) {
    const uid = user.uid;
    const userRef = firebase.database().ref('users/' + uid);

    userRef.on('value', (snapshot) => {
      const userData = snapshot.val();
      if (userData) {
        console.log("User Data:", userData);
        console.log("Username:", userData.username);
      } else {
        console.log("No user data found for this UID.");
      }
    }, (error) => {
      console.error("Error reading user data:", error);
    });
  } else {
    console.log("No user signed in to read data for.");
  }
</script>

Updating User Profile

Users might want to change their profile information. You can easily update specific fields within their UID's data path using the update() method.

This updates only the username field without affecting others.

<!-- Assume Firebase SDKs loaded & initialized -->

<script>
  const user = firebase.auth().currentUser;

  if (user) {
    const uid = user.uid;
    const userRef = firebase.database().ref('users/' + uid);

    userRef.update({
      username: "Jane_The_Explorer" // Update only username
    })
    .then(() => {
      console.log("Username updated successfully!");
    })
    .catch(error => {
      console.error("Error updating username:", error);
    });
  } else {
    console.log("No user signed in to update data for.");
  }
</script>

Handling Missing Data

It's important to always check if a user is signed in (firebase.auth().currentUser is not null) before trying to access their UID or database path.

Also, when reading data, check if snapshot.val() returns actual data or null. This prevents errors if a user's data hasn't been created yet.

Linking Best Practices

For efficiency and scalability, consider these tips:

Keep UIDs consistent: Always use the authenticated UID as the primary key for user data.
Denormalize for lookups: If you often need a user's name next to another piece of data (e.g., a post), store a copy of the name with the post instead of always querying the user profile.
Security Rules: Use Realtime Database Security Rules to enforce that only the authenticated user can read/write their own data. (More on this in a later lesson!)

Quick Check: User Data

You want to store a user's favorite color in the Realtime Database, ensuring it's linked to their authenticated profile. Which path correctly uses the user's UID as a key?

Recap: Connecting User Data

In this lesson, you learned how to effectively link authenticated users to their specific data in the Firebase Realtime Database.

We accessed the unique User ID (UID).
We used the UID as a key in the database path.
We practiced storing and reading user-specific information.
We covered important considerations for handling missing data.

This foundational skill is vital for building personalized and secure applications!

常见问题解答

「将用户数据连接到身份验证」课时是免费的吗？

是的 — 「将用户数据连接到身份验证」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 Firebase Auth & Realtime Database Apps 课程的其余内容，请升级到 CoddyKit PRO。 Firebase Auth & Realtime Database Apps 课程共包含 4 节课。

「将用户数据连接到身份验证」这节课中我会学到什么？

将已通过身份验证的用户 ID 与 Realtime Database 中对应的数据条目关联起来，以提供个性化内容你通过在浏览器中直接运行的动手代码来练习 Firebase Auth & Realtime Database Apps，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 Firebase Auth & Realtime Database Apps 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Firebase Auth & Realtime Database Apps 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 1 节课，共 4 节。

「将用户数据连接到身份验证」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 Firebase Auth & Realtime Database Apps 课中编写并运行代码吗？

能。每节 Firebase Auth & Realtime Database Apps 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。

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