/**
  * Adds new rate or updates existing one
  *
  * @param string $currencyFrom
  * @param string $currencyTo
  * @param float  $rate
  */
 protected function addUpdateExchangeRate($currencyFrom, $currencyTo, $rate)
 {
     if (!in_array($currencyTo, $this->managedCurrencies)) {
         return false;
     }
     $exchangeRate = $this->ratesRepository->findOneBy(['currencyFrom' => $currencyFrom, 'currencyTo' => $currencyTo]);
     if (null === $exchangeRate) {
         $exchangeRate = new CurrencyRate();
         $exchangeRate->setCurrencyFrom($currencyFrom);
         $exchangeRate->setCurrencyTo($currencyTo);
         $exchangeRate->setExchangeRate($rate);
         $this->helper->getEntityManager()->persist($exchangeRate);
     } else {
         $exchangeRate->setExchangeRate($rate);
     }
     return true;
 }