How to access the $container within middleware class in Slim v3?

Question

I've been reading that in Slim v2, $app was bound to the middleware class. I'm finding this not to be the case in v3? Below is my middleware class, but I'm just getting undefined:

<?php
namespace CrSrc\Middleware;

class Auth
{
    /**
     * Example middleware invokable class
     *
     * @param  \Psr\Http\Message\ServerRequestInterface $request  PSR7 request
     * @param  \Psr\Http\Message\ResponseInterface      $response PSR7 response
     * @param  callable                                 $next     Next middleware
     *
     * @return \Psr\Http\Message\ResponseInterface
     */
    public function __invoke($request, $response, $next)
    {
        // before

var_dump($this->getContainer()); // method undefined
var_dump($this->auth); exit; // method undefined
        if (! $this->get('auth')->isAuthenticated()) {
            // Not authenticated and must be authenticated to access this resource
            return $response->withStatus(401);
        }

        // pass onto the next callable
        $response = $next($request, $response);

        // after


        return $response;
    }
}

What's the correct way to access the DI container within middleware? I'm guessing there ought to be a way?

Raffish

Answer 1

A bit late to the party but might help others... You have to inject your container when instantiating the middleware

$container = $app->getContainer();
$app->add(new Auth($container));

And your middleware needs a constructor

<?php
namespace CrSrc\Middleware;

class Auth
{

    private $container;

    public function __construct($container) {
        $this->container = $container
    }

    /**
     * Example middleware invokable class
     *
     * @param  \Psr\Http\Message\ServerRequestInterface $request  PSR7 request
     * @param  \Psr\Http\Message\ResponseInterface      $response PSR7 response
     * @param  callable                                 $next     Next middleware
     *
     * @return \Psr\Http\Message\ResponseInterface
     */
    public function __invoke($request, $response, $next)
    {
        // $this->container has the DI

    }
}

LE: Expanding a bit the initial answer, the container gets injected in the constructor if you supply the middleware as a class string

$app->add('Auth');

or

$app->add('Auth:similarToInvokeMethod')

Peltate

Thanks. I think in the end I just assumed this was the way to go in v3. Seems to work well anyway. – Raffish

Great answer. A lot of people using Slimphp are looking for this answer but it is hidden behind the bushes known as Dependency Injection. Thanks! – Boling

Answer 2

As far as I understand the code, Slim (v3) works the following way:

• if you pass a closure as middleware, then it calls bindTo with container as param.

• if you pass a class/string that resolves to a class, then Slim creates the instance and passes the container as param to the constructor

  <?php
  $app->add(Auth);
  

• otherwise (e.g. if you add a middleware instance created earlier) then it looks like you have to take care of passing all necessary references.

Woodrow

This is partially correct: bindTo applies Closures when passed as middleware but if you pass a class it won't supply anything in the constructor – Peltate

@Peltate I just tested it with Slim 3.0.0 and adding middleware using $app->add(ClassName) created instance of ClassName supplying container as first param to the constructor. – Woodrow

that happens only if you supply the callable middleware as a string. It will go to CallableResolver::resolve and that method will instantiate your class. I guess the wrong statement is class/string ... it is really just string. – Peltate

For the test mentioned in previous comment I passed class name directly and not as a string. The thing is, calling $app->add(ClassName) PHP treats the param as string, because classes in PHP are not "first-class citizens". So it goes through the string path inside the CallableResolver::resolve. – Woodrow