實時傳播遠程配置更新

使用Cloud Functions for Firebase和FCM提供的 Remote Config 後台功能觸發，您可以實時傳播 Remote Config 更新。在這種情況下，您創建一個函數，當您從儀表板或 API 發布或回滾遠程配置模板時觸發。模板更新觸發發送 FCM 消息的函數，讓客戶端知道他們現有的配置已經過時，他們的下一次提取應該來自服務器：

本文檔的其餘部分將引導您完成這些步驟以實時傳播遠程配置更新。

將客戶端應用程序實例訂閱到 FCM 主題

為了將 FCM 消息定位到一大群客戶端應用程序實例（例如您的整個用戶群），主題消息傳遞是最有效的機制。每個應接收實時遠程配置更新的應用程序實例都必須訂閱主題名稱，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");
}
    

創建一個函數以在模板更新時發送 FCM ping

您可以觸發函數以響應遠程配置事件，包括發布新配置版本或回滾到舊版本。要實時傳播模板更新，請創建一個函數來偵聽模板發布事件，然後使用函數中的 FCM Admin SDK 向客戶端應用程序實例發送靜默 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;
  });
});

此函數設置一個CONFIG_STATE參數，然後將其作為 FCM 消息的數據負載發送給訂閱PUSH_RC主題的所有客戶端。

在客戶端設置遠程配置狀態

上一步中顯示的數據負載始終在應用程序的共享首選項中將CONFIG_STATE設置為STALE 。這表明已存儲在應用程序中的遠程配置模板現在已過時，因為創建了新的更新模板，其發布觸發了該功能。更新您的通知處理程序以測試此情況：

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();
    }
}
    

在應用程序啟動時獲取遠程配置更新

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"));
                }
            });
}
    

最後，向您的應用添加邏輯以強制從網絡獲取遠程配置（忽略本地存儲），因為CONFIG_STATE是STALE 。如果您的應用過於頻繁地從網絡中獲取數據，它可能會受到 Firebase 的限制。請參閱節流。