如何在Swift编写的iOS应用中基于FirebaseCloudMessaging实现用户间推送通知？

前置准备 #

• 确保iOS项目已完成Firebase SDK集成，开启Cloud Messaging功能，在Apple开发者后台配置推送证书并同步至Firebase控制台
• 客户端需获取用户的FCM Token，并与用户UID绑定存储到Firebase Firestore/Realtime Database中

实现流程 #

1. 客户端Token管理（Swift） #

负责获取、刷新并同步FCM Token到数据库，确保每个用户的Token是最新状态：

import FirebaseMessaging
import FirebaseAuth
import FirebaseFirestore

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        FirebaseApp.configure()
        // 获取初始FCM Token
        Messaging.messaging().token { token, error in
            guard let token = token, error == nil else {
                print("FCM Token获取失败: \(error?.localizedDescription ?? "未知错误")")
                return
            }
            self.syncTokenToFirestore(token: token)
        }
        // 监听Token刷新事件
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(tokenRefreshed),
            name: .messagingRegistrationTokenRefreshed,
            object: nil
        )
        return true
    }
    
    @objc private func tokenRefreshed() {
        guard let refreshedToken = Messaging.messaging().fcmToken else { return }
        syncTokenToFirestore(token: refreshedToken)
    }
    
    private func syncTokenToFirestore(token: String) {
        guard let uid = Auth.auth().currentUser?.uid else { return }
        let db = Firestore.firestore()
        db.collection("users").document(uid).setData(["fcmToken": token], merge: true) { error in
            if let error = error {
                print("Token同步失败: \(error.localizedDescription)")
            }
        }
    }
}

2. 服务端触发推送（Cloud Functions + Admin SDK） #

由于serverKey已废弃，必须使用Firebase Admin SDK发送推送。以下是通过Cloud Functions监听消息新增事件自动触发推送的示例（Node.js）：

const functions = require("firebase-functions");
const admin = require("firebase-admin");
admin.initializeApp();

// 监听messages集合的新增文档，触发推送
exports.sendUserNotification = functions.firestore.document("messages/{messageId}")
    .onCreate(async (snapshot) => {
        const messageData = snapshot.data();
        const recipientUid = messageData.recipientUid;
        const senderName = messageData.senderName;
        const content = messageData.content;

        // 获取接收方的FCM Token
        const userDoc = await admin.firestore().collection("users").document(recipientUid).get();
        if (!userDoc.exists || !userDoc.data().fcmToken) {
            functions.logger.error("接收方无有效FCM Token");
            return;
        }
        const targetToken = userDoc.data().fcmToken;

        // 构建推送 payload
        const payload = {
            notification: {
                title: `${senderName}的消息`,
                body: content,
                sound: "default"
            },
            token: targetToken
        };

        // 发送推送
        try {
            await admin.messaging().send(payload);
            functions.logger.info("推送发送成功");
        } catch (error) {
            functions.logger.error("推送发送失败: ", error);
        }
    });

客户端只需向messages集合写入包含recipientUid、senderName、content的文档，即可触发自动推送。

3. 客户端处理推送接收（Swift） #

处理前台展示、用户点击通知的逻辑：

import UserNotifications

extension AppDelegate: UNUserNotificationCenterDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 申请推送权限
        UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { granted, _ in
            if granted {
                DispatchQueue.main.async {
                    application.registerForRemoteNotifications()
                }
            }
        }
        UNUserNotificationCenter.current().delegate = self
        return true
    }

    // 前台收到通知时的展示逻辑
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.alert, .sound, .badge])
    }

    // 用户点击通知后的跳转逻辑
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        let userInfo = response.notification.request.content.userInfo
        // 根据userInfo中的参数跳转到对应聊天界面
        completionHandler()
    }
}

关键注意事项 #

• 禁止使用已废弃的serverKey，必须通过Firebase Admin SDK发送推送
• FCM Token会因重装应用、系统更新等情况变化，需确保实时同步到数据库
• Cloud Functions需配置正确的权限，确保能读取Firestore用户数据并调用Messaging API
• iOS 10+必须使用UserNotifications框架处理推送，不再支持旧的UIApplicationDelegate推送回调方法

内容的提问来源于stack exchange，提问作者user28587447