Please change the code in controller file as below

**From:**

```
protected $_postFactory;

    public function __construct(
        \Magento\Framework\App\Action\Context $context,
        \Magento\Framework\View\Result\PageFactory $pageFactory,
        \Softadroit\Prescription\Controller\Index $postFactory
        )
    {
        $this->_pageFactory = $pageFactory;
        $this->_postFactory = $postFactory;
        return parent::__construct($context);
    }
```

**To:**

```
    public function __construct(
        \Magento\Framework\App\Action\Context $context,
        \Magento\Framework\View\Result\PageFactory $pageFactory
        )
    {
        $this->_pageFactory = $pageFactory;
        return parent::__construct($context);
    }
```

After that run **php bin/magento setup:upgrade**
And then you can run **php bin/magento setup:di:compile**