Magento 2 custom API giving "Class string does not exist" error

Question

In Magento 2.4, I am using custom API and it is giving the below error.

{
"message": "Class string does not exist",
"code": -1
}

I have tried this and this solution. But nothing worked. Any solution for this?

• Zahid Hussain Magento: Can you share code?

Answer 1

I found the issue. In my case, It is due to the return type of the response specified in the Interface file(Usually at Api/Interface.php).

Sample code:

here it is: @return \Vendor\Module\Api\Data\ResponseDataInterface

<?php
namespace Vendor\Module\Api;
interface SampleInterface
{
/**
 * GET for Post api
 * @param string $customerId
 * @return \Vendor\Module\Api\Data\ResponseDataInterface
 */
public function getDetails($customerId);

}