Fatal Error Call to a member function dispatch() while call my Block in magento 2

Question

This is my Block File:

 <?php

 namespace ChennaiBox\Mymail\Block\Mail;

 class MailContent extends \Magento\Framework\View\Element\Template
 {
 protected $_objectManager;

 protected $customerSession;

 public function __construct(
    \Magento\Customer\Model\Session $customerSession,  
    \Magento\Framework\ObjectManagerInterface $objectManager
 ) {
    $this->customerSession = $customerSession;
    $this->_objectManager = $objectManager;
  }

 public function mymailData()
 {
try{

     if ($this->customerSession->isLoggedIn()) {
     $cutomerEmail    =(string)$this->customerSession->getCustomer()->getEmail();

     echo $cutomerEmail;

      else{
            $this->_redirect('customer/account/login/');
          }
   }catch (Exception $e) {

        $e->getMessage();

    }
   }

 }

If I call this block I get error

PHP Fatal error: Call to a member function dispatch() on null in /var/www/html/magento2/vendor/magento/framework/View/Element/AbstractBlock.php on line 642, referer: http://magentodev.gworks.mobi/magento2/customer/account/index/

from apache error.log file., why, suggect me how to solve this problem.

Answer 1

The problem is that your constructor does not match the parent class constructor.

To fix that you need to update your constructor:

public function __construct(
    \Magento\Framework\View\Element\Template\Context $context,
    \Magento\Customer\Model\Session $customerSession,  
    \Magento\Framework\ObjectManagerInterface $objectManager,
    array $data = []
 ) {
    parent::__construct($context, $data);
    $this->customerSession = $customerSession;
    $this->_objectManager = $objectManager;
  }

Don't forget to flush the var/cache and var/generation after your changes.