基于Firebase通知（Swift）实现单设备消息推送

Got it, let's walk through both how to send a push notification to a single iOS device via Firebase, and how to tie this to user-specific identifiers like phone numbers or usernames—this is totally doable, you just need to link those identifiers to the device's FCM token.

Firebase Cloud Messaging (FCM) identifies individual devices via a FCM Registration Token—this is the core of single-device pushes. Here's how to set it up:

Step 1: Get the FCM Token on iOS #

First, you need to fetch the device's FCM token in your iOS app (Swift example):

import FirebaseMessaging
import UserNotifications

class AppDelegate: UIResponder, UIApplicationDelegate, MessagingDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        FirebaseApp.configure()
        Messaging.messaging().delegate = self
        
        // Request notification permissions
        UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { granted, error in
            guard granted else { return }
            DispatchQueue.main.async {
                application.registerForRemoteNotifications()
            }
        }
        
        // Fetch initial token
        Messaging.messaging().token { token, error in
            if let error = error {
                print("Error fetching FCM token: \(error)")
            } else if let token = token {
                print("FCM Token: \(token)")
                // Save this token to your Firebase database (Firestore/Realtime DB)
                self.saveFCMTokenToDatabase(token: token)
            }
        }
        return true
    }
    
    // Listen for token updates (tokens can change when app is reinstalled, device is restored, etc.)
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
        guard let token = fcmToken else { return }
        print("FCM Token updated: \(token)")
        saveFCMTokenToDatabase(token: token)
    }
    
    // Helper to save token to Firestore
    private func saveFCMTokenToDatabase(token: String) {
        // Assuming you have a current user authenticated via Firebase Auth
        guard let userId = Auth.auth().currentUser?.uid else { return }
        
        let db = Firestore.firestore()
        db.collection("users").document(userId).updateData([
            "fcmToken": token
        ]) { error in
            if let error = error {
                print("Error saving token: \(error)")
            }
        }
    }
}

Step 2: Send a Push to the Token #

Once the token is stored, you have two reliable ways to send a push:

• Firebase Console: Head to Firebase Console > Cloud Messaging > New Notification. Under "Target", select "Single device" and paste the FCM token you saved.
• Firebase Admin SDK (ideal for server-side/automated pushes):
  Here's a Node.js example:

  const admin = require('firebase-admin');
  admin.initializeApp();
  
  const sendSingleDevicePush = async (token) => {
      const message = {
          notification: {
              title: "Hey there!",
              body: "This is a test push to your specific device"
          },
          token: token
      };
  
      try {
          const response = await admin.messaging().send(message);
          console.log("Successfully sent message:", response);
      } catch (error) {
          console.log("Error sending message:", error);
      }
  };
  
  // Call with the stored token from your database
  sendSingleDevicePush("YOUR_DEVICE_FCM_TOKEN");
  

To push via phone number, username, or other custom identifiers, you just need to create a mapping between that identifier and the user's FCM token in your database. Here's the step-by-step:

Step 1: Link User Identifiers to FCM Tokens #

When a user signs up or logs in, store their phone number/username alongside their FCM token in your database. For example, in Firestore, your users collection documents might look like:

users/{userId}
  - phoneNumber: "+1234567890"
  - username: "matthewcho"
  - fcmToken: "DEVICE_FCM_TOKEN_HERE"
  - ... other user profile data

Update your iOS app's saveFCMTokenToDatabase function to include these identifiers when saving/updating the token.

Step 2: Fetch the Token by User Identifier (Server-Side) #

Use the Firebase Admin SDK to query your database for the token associated with the user's phone number/username. Example in Node.js:

const getTokenByPhoneNumber = async (phoneNumber) => {
    const db = admin.firestore();
    const snapshot = await db.collection("users").where("phoneNumber", "==", phoneNumber).get();
    
    if (snapshot.empty) {
        console.log("No user found with that phone number");
        return null;
    }
    
    // Assuming one user per phone number (adjust to an array if multiple devices are allowed)
    const userDoc = snapshot.docs[0];
    return userDoc.data().fcmToken;
};

Step 3: Send the Push to the Fetched Token #

Combine the above with the send function we wrote earlier:

const sendPushByPhoneNumber = async (phoneNumber) => {
    const token = await getTokenByPhoneNumber(phoneNumber);
    if (token) {
        await sendSingleDevicePush(token);
    }
};

// Call with the target user's phone number
sendPushByPhoneNumber("+1234567890");

Key Notes to Avoid Headaches #

• Handle multiple devices: If a user uses multiple devices, store an array of FCM tokens instead of a single string, then loop through them to send pushes to all their devices.
• Token freshness: Always listen for token updates (as shown in the iOS code) and update your database immediately—FCM tokens can expire or change when an app is reinstalled or a device is restored, so stale tokens will fail to deliver pushes.
• Security: Lock down your database rules to restrict access to user token data (e.g., only allow authenticated admins to query tokens by phone number/username).

内容的提问来源于stack exchange，提问作者Matthew Cho