Return bool gives error "Invalid return type" for Ajax Controller

Question

I want to call this controller through Ajax and have it return true or false. the methods all work correctly, however I get the error

Invalid return type C:\Sites\retracted\wwwroot\vendor\magento\framework\App\Bootstrap.php(258): Magento\Framework\App\Http->launch()

So I assume with extends Action I can't simply return a boolean - but what should it be to allow me to return a bool?

use \Magento\Framework\App\Action\Action;

class IsEmailRegistered extends Action implements \Magento\Framework\DataObject\IdentityInterface
{

    ...

    public function execute()
    {
        $result = $this->voucherHelper->validateEmail($email);

        return $result;
    }
}

Answer 1

Try this example:

protected $resultJsonFactory;

/**
 * @param Context $context
 * @param \Magento\Framework\Controller\Result\JsonFactory $resultJsonFactory
 */
public function __construct(
    Context $context,
    \Magento\Framework\Controller\Result\JsonFactory $resultJsonFactory
)
{
    $this->resultJsonFactory = $resultJsonFactory;
    parent::__construct($context);
}

/**
 * Collect relations data
 *
 * @return \Magento\Framework\Controller\Result\Json
 */
public function execute()
{
    $result = $this->voucherHelper->validateEmail($email);
    /** @var \Magento\Framework\Controller\Result\Json $result */
    $resultJson = $this->resultJsonFactory->create();

    return $resultJson->setData(['success' => $result]);
}

But in your code you should parse the answer as JSON.