How To Override Custom Module Helper in Magento 2

Question

I would need to override the custom module helper into my custom module.

Custom module code was,

class Data extends AbstractHelper
{
 const XML_PATH_BLOG = 'blog/';
 protected $storeManager;
 protected $objectManager;
 protected $postfactory;
 protected $categoryfactory;
 protected $tagfactory;
 protected $topicfactory;
 protected $scopeConfig;
 public function __construct(
 Context $context,
 ObjectManagerInterface $objectManager,
 StoreManagerInterface $storeManager,
 PostFactory $postFactory,
 CategoryFactory $categoryFactory,
 TagFactory $tagFactory,
 TopicFactory $topicFactory,
 ScopeConfigInterface $scopeConfig
 )
 {
 $this->objectManager = $objectManager;
 $this->storeManager = $storeManager;
 $this->postfactory = $postFactory;
 $this->categoryfactory = $categoryFactory;
 $this->tagfactory = $tagFactory;
 $this->topicfactory = $topicFactory;
 $this->scopeConfig = $scopeConfig;
 parent::__construct($context);
 }

My overriding code was,

class Resize extends \Mageplaza\Blog\Helper\Data
{
 protected $_filesystem;
 protected $_directory;
 protected $_imageFactory;
 protected $_storeManager;
 public function __construct(
 StoreManagerInterface $storeManager,
 \Magento\Framework\Filesystem $filesystem,
 \Magento\Framework\Image\AdapterFactory $imageFactory
 )
 {
 $this->_storeManager = $storeManager;
 $this->_filesystem = $filesystem;
 $this->_imageFactory = $imageFactory;
 $this->_directory = $filesystem->getDirectoryWrite(DirectoryList::MEDIA);
 }

Am I missed anything here? Because, it throws the following error when I was calling the method called getConfigValue() as follow:

Fatal error: Call to a member function getValue() on null in E:\xxxamp\htdocs\accelerator\app\code\Mageplaza\Blog\Helper\Data.php on line 50

public function getConfigValue($field, $storeId = null)
{
 return $this->scopeConfig->getValue($field, \Magento\Store\Model\ScopeInterface::SCOPE_STORE);
}

Answer 1

Your constructor in the Resize class should look like this:

public function __construct(
 Context $context,
 ObjectManagerInterface $objectManager,
 StoreManagerInterface $storeManager,
 PostFactory $postFactory,
 CategoryFactory $categoryFactory,
 TagFactory $tagFactory,
 TopicFactory $topicFactory,
 ScopeConfigInterface $scopeConfig,
 \Magento\Framework\Filesystem $filesystem,
 \Magento\Framework\Image\AdapterFactory $imageFactory
)
{
 $this->_filesystem = $filesystem;
 $this->_imageFactory = $imageFactory;
 $this->_directory = $filesystem->getDirectoryWrite(DirectoryList::MEDIA);
 parent::__construct($context, $objectManager, $storeManager, $postFactory, $categoryFactory, $tagFactory, $topicFactory, $scopeConfig);
}

• TS Guhan: Yes it is correct. I didn't get any error now.
• TS Guhan: Marius, can you please tell me why should we pass the objects in __contruct(???). Because, In some cases we are not passing those objects.
• Marius: this is how Dependency Injection works in M2. You have to supply in the class constructor all the dependencies it needs. And Magento will take care of instantiating them.