实时传播远程配置更新

使用Cloud Functions for Firebase和FCM提供的 Remote Config 后台功能触发，您可以实时传播 Remote Config 更新。在这种情况下，您创建一个函数，当您从仪表板或 API 发布或回滚远程配置模板时触发。模板更新触发发送 FCM 消息的函数，让客户端知道他们现有的配置已经过时，他们的下一次提取应该来自服务器：

本文档的其余部分将引导您完成这些步骤以实时传播远程配置更新。

将客户端应用程序实例订阅到 FCM 主题

为了将 FCM 消息定位到一大群客户端应用程序实例（例如您的整个用户群），主题消息传递是最有效的机制。每个应接收实时远程配置更新的应用程序实例都必须订阅主题名称，例如PUSH_RC ：

extension AppDelegate : MessagingDelegate {
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
        messaging.subscribe(toTopic: "PUSH_RC") { error in
            print("Subscribed to PUSH_RC topic")
        }
    }
}
    

- (void)messaging:(FIRMessaging *)messaging didReceiveRegistrationToken:(NSString *)fcmToken {
    [[FIRMessaging messaging] subscribeToTopic:@"PUSH_RC" completion:^(NSError * _Nullable error) {
        NSLog(@"Subscribed to PUSH_RC topic");
    }];
}
    

@Override
public void onNewToken(String s) {
    FirebaseMessaging.getInstance().subscribeToTopic("PUSH_RC");
}
    

创建一个函数以在模板更新时发送 FCM ping

您可以触发函数以响应远程配置事件，包括发布新配置版本或回滚到旧版本。要实时传播模板更新，请创建一个函数来侦听模板发布事件，然后使用函数中的 FCM Admin SDK 向客户端应用程序实例发送静默 ping：

exports.pushConfig = functions.remoteConfig.onUpdate(versionMetadata => {
  // Create FCM payload to send data message to PUSH_RC topic.
  const payload = {
    topic: "PUSH_RC",
    data: {
      "CONFIG_STATE": "STALE"
    }
  };
  // Use the Admin SDK to send the ping via FCM.
  return admin.messaging().send(payload).then(resp => {
    console.log(resp);
    return null;
  });
});

此函数设置一个CONFIG_STATE参数，然后将其作为 FCM 消息的数据负载发送给订阅PUSH_RC主题的所有客户端。

在客户端设置远程配置状态

上一步中显示的数据负载始终在应用程序的共享首选项中将CONFIG_STATE设置为STALE 。这表明已存储在应用程序中的远程配置模板现在已过时，因为创建了新的更新模板，其发布触发了该功能。更新您的通知处理程序以测试此情况：

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
                 fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

    if (userInfo.index(forKey: "CONFIG_STATE") != nil) {
        print("Config set to stale")
        UserDefaults.standard.set(true, forKey:"CONFIG_STALE")
    }

    completionHandler(UIBackgroundFetchResult.newData)
}
    

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {

    if (userInfo[@"CONFIG_STATE"]) {
        NSLog(@"Config set to stale");
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"CONFIG_STALE"];
    }

    completionHandler(UIBackgroundFetchResultNewData);
}
    

@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
    if (remoteMessage.getData().containsKey("CONFIG_STATE")) {
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
        sharedPreferences.edit().putBoolean("CONFIG_STALE", true).apply();
    }
}
    

在应用程序启动时获取远程配置更新

func fetchConfig() {
  welcomeLabel.text = remoteConfig[loadingPhraseConfigKey].stringValue

  var expirationDuration = 3600
  // If your app is using developer mode, expirationDuration is set to 0, so each fetch will
  // retrieve values from the service.
  if remoteConfig.configSettings.isDeveloperModeEnabled || UserDefaults.standard.bool(forKey: "CONFIG_STALE") {
    expirationDuration = 0
  }

  remoteConfig.fetch(withExpirationDuration: TimeInterval(expirationDuration)) { (status, error) -> Void in
    if status == .success {
      print("Config fetched!")
      self.remoteConfig.activateFetched()
    } else {
      print("Config not fetched")
      print("Error: \(error?.localizedDescription ?? "No error available.")")
    }
    self.displayWelcome()
  }
}
    

- (void)fetchConfig {
    self.welcomeLabel.text = self.remoteConfig[kLoadingPhraseConfigKey].stringValue;

    long expirationDuration = 3600;
    // If your app is using developer mode, expirationDuration is set to 0, so each fetch will
    // retrieve values from the Remote Config service.
    if (self.remoteConfig.configSettings.isDeveloperModeEnabled || [[NSUserDefaults standardUserDefaults] boolForKey:@"CONFIG_STALE"]) {
        expirationDuration = 0;
    }

    [self.remoteConfig fetchWithExpirationDuration:expirationDuration completionHandler:^(FIRRemoteConfigFetchStatus status, NSError *error) {
        if (status == FIRRemoteConfigFetchStatusSuccess) {
            NSLog(@"Config fetched!");
            [self.remoteConfig activateFetched];
            [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"CONFIG_STALE"];
        } else {
            NSLog(@"Config not fetched");
            NSLog(@"Error %@", error.localizedDescription);
        }
        [self displayWelcome];
    }];
}
    

private void fetchWelcomeMessage() {
    mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("loading_phrase"));

    long cacheExpiration = 43200; // 12 hours in seconds.
    // If your app is using developer mode or cache is stale, cacheExpiration is set to 0,
    // so each fetch will retrieve values from the service.
    if (mFirebaseRemoteConfig.getInfo().getConfigSettings().isDeveloperModeEnabled() ||
            mSharedPreferences.getBoolean("CONFIG_STALE", false)) {
        cacheExpiration = 0;
    }

    mFirebaseRemoteConfig.fetch(cacheExpiration)
            .addOnCompleteListener(this, new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Toast.makeText(MainActivity.this, "Fetch Succeeded",
                                Toast.LENGTH_SHORT).show();

                        // After config data is successfully fetched, it must be activated before newly fetched
                        // values are returned.
                        mFirebaseRemoteConfig.activateFetched();
                    } else {
                        Toast.makeText(MainActivity.this, "Fetch Failed",
                                Toast.LENGTH_SHORT).show();
                    }
                    mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("welcome_message"));
                }
            });
}
    

最后，向您的应用添加逻辑以强制从网络获取远程配置（忽略本地存储），因为CONFIG_STATE是STALE 。如果您的应用过于频繁地从网络中获取数据，它可能会受到 Firebase 的限制。请参阅节流。