Middleware

Middleware lets you inspect and filter navigation requests before they reach a route, making it the right place for authentication guards, permission checks, and pre-navigation side effects.

• Introduction
• Generating Middleware
• Defining Middleware
• Registering Middleware
  • Global Middleware
  • Assigning Middleware To Routes
• Middleware & Responses
• Authorization Middleware

Introduction

Middleware provide a convenient mechanism for inspecting and filtering navigation requests entering your application. For example, Magic includes a middleware that verifies the user is authenticated. If the user is not authenticated, the middleware will redirect the user to your application's login screen. However, if the user is authenticated, the middleware will allow the request to proceed further into the application.

Of course, additional middleware can be written to perform a variety of tasks besides authentication. Middleware are stored in the lib/app/middleware directory.

Generating Middleware

Use the Magic CLI to generate a new middleware class:

dart run magic:artisan make:middleware Auth

This creates lib/app/middleware/auth.dart with a MagicMiddleware stub ready to implement.

Defining Middleware

To create a new middleware, create a class that extends MagicMiddleware:

import 'package:magic/magic.dart';

class EnsureAuthenticated extends MagicMiddleware {
  @override
  String? redirectTarget(String location) {
    if (!Auth.check() && location != '/login') return '/login';
    return null; // Authenticated, or already on /login: allow.
  }
}

As you can see, if the user is not authenticated, the middleware returns the login path and the user is redirected to the login screen. If the user is authenticated, it returns null and the request proceeds.

Redirect guards vs blocking guards

Middleware has two hooks, and you pick the one that matches the intent:

• redirectTarget(String location) for redirect-style guards (auth, guest, role gates). It is evaluated synchronously in the router's redirect callback BEFORE the route builds, so the destination view mounts exactly once. Return a path to redirect to, or null to allow. Always return null when location already equals the target, otherwise the redirect loops.
• handle(void Function() next) for async, non-redirecting concerns (logging, a blocked-state screen). Call next() to allow, skip it to block. Both hooks default to allow, so override only the one you need.

[!IMPORTANT] Prefer redirectTarget for redirects. Redirecting with an imperative MagicRoute.to() from inside handle() runs after the route has already mounted, so it remounts the destination view and recreates its state.

Async Operations

All middleware is asynchronous. You may perform await operations before deciding whether to call next():

class TeamAccessMiddleware extends MagicMiddleware {
  @override
  Future handle(void Function() next) async {
    final team = await Team.find(Request.route('teamId'));
    
    if (team != null && team.hasMember(Auth.id())) {
      next();
    } else {
      MagicRoute.to('/unauthorized');
    }
  }
}

Registering Middleware

Global Middleware

If you want middleware to run during every navigation in your application, register it globally in your lib/app/kernel.dart:

void registerKernel() {
  Kernel.global([
    () => LoggingMiddleware(),
    () => VerifyDeviceMiddleware(),
  ]);
}

Global middleware runs on every route, in the order they are registered.

Assigning Middleware To Routes

To assign middleware to specific routes, first register it with a key in your Kernel:

void registerKernel() {
  Kernel.registerAll({
    'auth': () => EnsureAuthenticated(),
    'guest': () => RedirectIfAuthenticated(),
    'admin': () => EnsureAdmin(),
  });
}

Then use the string key in your route definitions:

// Single middleware
MagicRoute.page('/dashboard', () => DashboardView())
    .middleware(['auth']);

// Multiple middleware (executed in order)
MagicRoute.page('/admin', () => AdminPanel())
    .middleware(['auth', 'admin']);

An alias nothing registered stops the app at Magic.init, rather than leaving the route ungated:

StateError: Unresolvable route middleware on 1 route:
  /admin: Route middleware alias "admin" is not registered. Register it with
  Kernel.register('admin', () => ...) from a service provider.

The router checks every registered route's middleware when it builds, which is step 7 of Magic.init, after every provider has booted. So an alias registered from register() or from boot() is equally early, and the usual cause of this error is a typo or an alias nobody registered at all.

Every registered route includes the ones declared inside a layout. A route in MagicRoute.group(layout: ...) or MagicRoute.layout(...) is held in the layout's own child list rather than the top-level table, and a shell or tab layout is where a gated screen usually lives, so the check walks both.

Bootstrap rather than navigation is deliberate. Kernel.resolveAll throws at navigation too, but that throw happens inside GoRouter's redirect callback, which routes it to onException: the page renders nothing and the log reports a routing failure, which names the wrong problem.

Route Group Middleware

You can apply middleware to all routes within a group:

MagicRoute.group(
  middleware: ['auth'],
  routes: () {
    MagicRoute.page('/dashboard', () => DashboardView());
    MagicRoute.page('/profile', () => ProfileView());
    MagicRoute.page('/settings', () => SettingsView());
  },
);

Middleware & Responses

Since middleware controls navigation flow, there are two possible outcomes:

Action	Effect
Call next()	Navigation proceeds to the route
Don't call next()	Navigation is blocked

When blocking, you should redirect the user:

@override
Future handle(void Function() next) async {
  if (await hasValidSubscription()) {
    next();
  } else {
    // Don't call next() - redirect instead
    MagicRoute.to('/subscription/required');
    Magic.error('Subscription Required', 'Please upgrade your plan.');
  }
}

Authorization Middleware

Magic includes AuthorizeMiddleware that integrates with the Gate authorization system—equivalent to Laravel's can middleware.

Basic Usage

Register authorization middleware in your Kernel:

void registerKernel() {
  Kernel.registerAll({
    'auth': () => EnsureAuthenticated(),
    'can:manage-team': () => AuthorizeMiddleware('manage-team'),
    'can:admin': () => AuthorizeMiddleware('admin-access'),
  });
}

Use in your routes:

MagicRoute.page('/team/settings', () => TeamSettings())
    .middleware(['auth', 'can:manage-team']);

MagicRoute.page('/admin', () => AdminPanel())
    .middleware(['auth', 'can:admin']);

Custom Redirect

By default, unauthorized users are redirected to /unauthorized. Customize this:

Kernel.register('can:admin', () => AuthorizeMiddleware(
  'admin-access',
  unauthorizedRoute: '/access-denied',
));

With Model Arguments

For authorization requiring a model (like checking ownership), create a custom middleware:

class CanEditPostMiddleware extends MagicMiddleware {
  @override
  Future handle(void Function() next) async {
    final postId = Request.route('id');
    final post = await Post.find(postId);

    if (post != null && Gate.allows('edit-post', post)) {
      next();
    } else {
      MagicRoute.to('/unauthorized');
    }
  }
}

Register and use it:

Kernel.register('can:edit-post', () => CanEditPostMiddleware());

MagicRoute.page('/posts/:id/edit', (id) => EditPostView(id: id))
    .middleware(['auth', 'can:edit-post']);

See the Authorization documentation for more on defining abilities and policies.