Question related to WiFi.scan callback

WiFiManager.h

class WiFiManager {

	public:
	
		boolean isWiFiDirectFlag = false;
		boolean isNoWiFiFlag     = false;
		boolean isWiFiDirectRunningFor60Seconds = false;

		// global because accessible from wifi_scan_callback and isStoredSSIDAvailable functions.
		// we always set this, because maybe on the road WAPs will be added (without a reset)
		WiFiAccessPoint storedWAPs[5];
		int             storedWAPsAmount = 0;
		bool            isStoredSSIDFound = false;

		//enum WiFiManagerState { RSSIINDICATORSTATE_CHECK, RSSIINDICATORSTATE_ON, RSSIINDICATORSTATE_ON_WAIT, RSSIINDICATORSTATE_OFF_WAIT, RSSIINDICATORSTATE_CHECK_WAIT };

		WiFiManager();
		virtual ~WiFiManager();

		void setup();

		void loop();

		void wifi_scan_callback(WiFiAccessPoint*, void*);

		bool isStoredSSIDAvailable();

	//private:
	
};

// end class initialisation


WiFiManager::WiFiManager() {
}

WiFiManager::~WiFiManager() {
}//

void WiFiManager::setup() {
	Serial.println("hi");

}

void WiFiManager::loop() {
	//delay(1000);

}

void WiFiManager::wifi_scan_callback(WiFiAccessPoint* wap, void* data)
{
    WiFiAccessPoint& ap = *wap;

    for (int i = 0; i < storedWAPsAmount; i++){
        if (strcmp(ap.ssid, storedWAPs[i].ssid) == 0) {
          isStoredSSIDFound = true;
          Serial.print("SSID: ");
          Serial.println(ap.ssid);
          Serial.print("Security: ");
          Serial.println(ap.security);
          Serial.print("Channel: ");
          Serial.println(ap.channel);
          Serial.print("RSSI: ");
          Serial.println(ap.rssi);
        }
    }
}

bool WiFiManager::isStoredSSIDAvailable() {

  // in the callback we compare scanned WAPs with the stored WAPs
  // storedSSIDFound will be set to true if we have a match
  // this is global so we can access this after a call to this function

  isStoredSSIDFound = false;

	//WiFi.scan(&WiFiManager::wifi_scan_callback);
	WiFi.scan(&wifi_scan_callback);

  return isStoredSSIDFound;
  //int scannedWAPsAmount =
  //Serial.print(scannedWAPsAmount);
  //Serial.println(" APs scanned and compared.");
}