Magento 2 Full Page Cache not working

Question

Whenver I turn on FPC(Full Page Cache) feature in my Magento CE 2.0.2 site (doesn't matter if default theme or custom theme is running.) and when I open the Homepage of this site, then it gives "Internal Server Error 500" in the Firefox console, and the page is blank.

What could be the possible issue ?

Answer 1

We had the same issue after enabling FPC. The following error would occur:

Fatal error: Uncaught Error: Call to a member function getIdentities() on null in /vendor/magento/module-catalog/Block/Category/View.php:177 

Not the most helpful error message but after some digging we found that this was being triggered by using the block type Magento\Catalog\Block\Category\View on our homepage - presumably because there is no category initialised at that point.

This was a coding error by one of our developers as this particular block did not need that type and was fine with just Magento\Framework\View\Element\Template which is the Magento 2 equivalent of core/template.

Answer 2

---

rewrite the function like this to handle the null values:

---

public function getIdentities()
    {
        $identities = [];

        if (is_array($this->getItems()) || is_object($this->getItems()))
        {
            foreach ($this->getItems() as $item)
            {
                $identities = array_merge($identities, $item->getIdentities());
            }
        }
        return $identities;

}