In magento2,How to inject helper in collection

Question

I have created a custom grid, in this grid collection I have to inject helper .while injecting helper in the collection it throws error like this Type Error occurred when creating object:

My collection:

namespace vendor\module\Model\ResourceModel\Post;

use \Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection;

    class Collection extends AbstractCollection
    {
        /**
         * Define model & resource model
         */
        const YOUR_TABLE = 'xxx';


        protected $helper;
        public function __construct(
            \Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
            \Psr\Log\LoggerInterface $logger,
            \vendor\magento\Helper\Userdata $helper,
            \Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
            \Magento\Framework\Event\ManagerInterface $eventManager,
            \Magento\Store\Model\StoreManagerInterface $storeManager,
            \Magento\Framework\DB\Adapter\AdapterInterface $connection = null,
            \Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
        ) {
            $this->_init(
                ' vendor\module\Model\Post', ' vendor\module\Model\ResourceModel\Post'
            );
            parent::__construct(
                $entityFactory, $logger, $fetchStrategy, $eventManager, $connection,$resource,$helper
            );
            $this->storeManager = $storeManager;

        }
        protected function _initSelect()
        {
            parent::_initSelect();

            $this->getSelect()->where("main_table.user_id = 2";
        }

Answer 1

public function __construct(
    \Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
    \Psr\Log\LoggerInterface $logger,
    \Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
    \Magento\Framework\Event\ManagerInterface $eventManager,
    \Vendor\Module\Helper\YourHelperClass $helper,  
    \Magento\Framework\DB\Adapter\AdapterInterface $connection = null,
    \Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
) {
    $this->helper = $helper;
    parent::__construct(
        $entityFactory, $logger, $fetchStrategy, $eventManager, $connection,
        $resource
    );
}

protected function _construct()
{
    $this->_init(
        'Vendor\Module\Model\Post', ' vendor\module\Model\ResourceModel\Post'
    );
}

Answer 2

Inject your helper before below line

\Magento\Framework\DB\Adapter\AdapterInterface $connection = null as below

public function __construct(
    \Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
    \Psr\Log\LoggerInterface $logger,
    \Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
    \Magento\Framework\Event\ManagerInterface $eventManager,
    \Magento\Store\Model\StoreManagerInterface $storeManager,
    \NameSpace\Module\Helper\YourHelperClass  
    \Magento\Framework\DB\Adapter\AdapterInterface $connection = null,
    \Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
) {
    $this->_init(
        ' vendor\module\Model\Post', ' vendor\module\Model\ResourceModel\Post'
    );
    parent::__construct(
        $entityFactory, $logger, $fetchStrategy, $eventManager, $connection,
        $resource
    );
    $this->storeManager = $storeManager;

}