Another cool feature of WP-FastEndpoints is the support for middlewares.

Middlewares are pieces of code that can either run before and/or after a request is handled.

At this stage, you might be already familiar with returns(...) which is a middleware.
However, you can also create your own.

<?php
use Attributes\Wp\FastEndpoints\Contracts\Middleware;

class MyCustomMiddleware extends Middleware
{
    /**
    * This function is triggered before the main handler runs
    * but after checking the user permissions.
    */
    public function onRequest(/* (1) */)) {
        return; /* (2) */
    }
    
    /**
    * This function is triggered after the main handler,
    * before sending a response to the client 
    */
    public function onResponse(/* (3) */) {
        return; /* (4) */
    }
}

$router->get('/test', function () {
    return true;
})
->middleware(new MyCustomMiddleware());

1. Supports all features that a regular endpoint supports
   e.g. injectables,
   typed request data
2. Early response return is also supported. See Responses page
3. Middlewares supports all features that a regular endpoint supports
   e.g. injectables,
   typed request data
4. Early response return is also supported. See Responses page