Magento 2.2.6 – Uncaught Error: Undefined Class Constant ‘CACHE_TAG’

crudmagento2magento2.2.6

I am very new to Magento, i created a CRUD custom module, when I input some data in form, and hit save button, I got an error like this:

Fatal error: Uncaught Error: Undefined class constant 'CACHE_TAG' in
C:\xampp\htdocs\test-local\app\code\Testing\SimpleNews\Model\News.php:9
Stack trace: #0 C:\xampp\htdocs\test-local\vendor\magento\framework\App\Cache\Tag\Strategy\Identifier.php(25):Testing\SimpleNew\Mode\News->getIdentities() 
#1 C:\xampp\htdocs\test-local\vendor\magento\framework\App\Cache\Tag\Resolver.php(43): Magento\Framework\App\Cache\Tag\Strategy\Identifier->getTags(Object(Testing\SimpleNews\Model\News)) 
#2 C:\xampp\htdocs\test-local\vendor\magento\module-page-cache\Observer\FlushCacheByTags.php(64): Magento\Framework\App\Cache\Tag\Resolver->getTags(Object(Testing\SimpleNews\Model\News)) 
#3 C:\xampp\htdocs\test-local\vendor\magento\framework\Event\Invoker\InvokerDefault.php(72): Magento\PageCache\Observer\FlushCacheByTags->execute(Object(Magento\Framework\Event\Observer)) 
#4 C:\xampp\htdocs\test-local\vendor\magento\framework\Event\Invoker\InvokerDefault.php(60): Magento\Framework\Event\Invoker\InvokerDefault->_callObserverMethod(Object(Magento\ in C:\xampp\htdocs\test-local\app\code\Testing\SimpleNews\Model\News.php on line 9

This is my htdocs\test-local\app\code\Testing\SimpleNews\Model\News.php code:

<?php

namespace Testing\SimpleNews\Model;

class News extends \Magento\Framework\Model\AbstractModel implements \Magento\Framework\DataObject\IdentityInterface
{
    public function getIdentities()
    {
        return [self::CACHE_TAG . '_' . $this->getId()];
    }

    public function getDefaultValues()
    {
        $values = [];

        return $values;
    }

    /**
     * Define resource model
     */
    protected function _construct()
    {
        $this->_init('Testing\SimpleNews\Model\Resource\News');
    }
}

Best Answer

In the function getIdentities() in your class you can see that the class constant CACHE_TAG is being used. You can read all about class constants here:

I would suggest defining it at the top of your class, this cache tag let's magento know where to store cached data. An example would be: 

namespace Testing\SimpleNews\Model;

class News extends \Magento\Framework\Model\AbstractModel implements \Magento\Framework\DataObject\IdentityInterface
{
    const CACHE_TAG = 'TESTING_SIMPLE_NEWS';

    public function getIdentities()
    {
        return [self::CACHE_TAG . '_' . $this->getId()];
    }

    public function getDefaultValues()
    {
        $values = [];

        return $values;
    }

    /**
     * Define resource model
     */
    protected function _construct()
    {
        $this->_init('Testing\SimpleNews\Model\Resource\News');
    }
}
Related Topic