$request->code 

Middleware parameters

Middleware can also receive additional custom parameters. For example, if your app needs to verify that the user has a given "role" before executing an action, you can create a RoleMiddleware middleware that accepts the role name as an extra parameter.

Extra parameters of the middleware will be passed in after the $next parameter:

<?php

namespace App\Http\Middleware;

use Closure;

class RoleMiddleware
{
    /**
     * Run the request filter.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @param  string  $role
     * @return mixed
     */
    public function handle($request, Closure $next, $role)
    {
        if (! $request->user()->hasRole($role)) {
            // Redirect...
        }

        return $next($request);
    }

}

Middleware parameters can be specified by separating the name and parameters of the middleware with : when defining routes. Multiple parameters should be separated by commas:

Route::put('post/{id}', ['middleware' => 'role:editor', function ($id) {
    //
}]);

For details, please refer to: http://www.golaravel.com/laravel/docs/5.1/middleware/#middleware-parameters