Dependency injection

Handler parameters can include a request, a form request, or services:

public function handle(MessageRequest $request, MessageService $messages): array
{
    return $messages->process($request->validated());
}

Here, MessageService is an application service you define and import. Bind interfaces in Laravel's container when needed. Contextual bindings for the action are supported during normal dispatch and Precognition dependency resolution.

Constructor injection is supported too. Keep constructors free of writes and other side effects: the action is created before method checks and action middleware. Constructors also run when exert:list resolves classes. Dependencies that require an action middleware's user or tenant context should be resolved in handle() after that middleware runs.

Scalar parameters are not filled from request input. They may receive a same-named route parameter, but handle(string $email) does not read an email body or query field automatically. Read validated input from a request instead. See Route parameters for route-value injection.

Bind an interface for one action

Sometimes two actions need different implementations of the same interface. Laravel's contextual binding lets you describe that choice in an application provider:

use App\Contracts\ReceiptSender;
use App\Http\Actions\Orders\SendReceipt;
use App\Services\EmailReceiptSender;

$this->app->when(SendReceipt::class)
    ->needs(ReceiptSender::class)
    ->give(EmailReceiptSender::class);

These are application types: define the interface, implementation, and action before using this snippet. The action can then ask for ReceiptSender in handle().

Exert preserves this resolution context during predictions too. A contextual FormRequest replacement therefore keeps its validation and authorization rules in both request types.

Constructors run earlier than you might expect

If action middleware signs in a user or selects a tenant, an action constructor has already run by then. A constructor should not assume that action middleware has prepared those values.

Prefer resolving such dependencies in the handler, or move shared setup to route middleware. The lifecycle page shows the exact order.

Method bindings are an advanced case

Normal dispatch honors Laravel container method bindings for handle(). Prediction resolves the declared handler dependencies but intentionally does not execute a method binding. A binding may do real work, so it is not a validation hook.

Put prediction rules in an injected form request. Do not hide essential validation only inside a method binding.