protected function getQuoteStrategy()
    {
        if (!$this->quoteStrategy instanceof QuoteStrategy) {
            $quoteStrategy = $this->getOption('quote_strategy');

            if (!$quoteStrategy instanceof QuoteStrategy) {
                $quoteStrategy = new DefaultQuoteStrategy;
            }

            $this->quoteStrategy = $quoteStrategy;
        }

        return $this->quoteStrategy;
    }