public function setCache(\Psr\SimpleCache\CacheInterface $cache, $key, $ttl = 86400)
    {
        $this->cache = $cache;
        $this->cacheKey = $key;
        $this->cacheTime = $ttl;

        if (empty($this->cacheKey))
        {
            $this->cacheKey = 'concatenate-'.md5(serialize($this));
        }

        return $this;
    }