Our package supports a simple command bus implementation that's able to automatically map commands to aggregate roots. If you want to use dedicated command objects, this can be a useful feature in order to prevent much boilerplate for writing command handlers. It's also possible to manually create command handlers if you want to.
A command looks like this:
namespace Spatie\Shop\Cart\Commands;
use Spatie\Shop\Support\EventSourcing\Attributes\AggregateUuid;
use Spatie\Shop\Support\EventSourcing\Attributes\HandledBy;
use Spatie\Shop\Support\EventSourcing\Commands\Command;
#[HandledBy(CartAggregateRoot::class)]
class AddCartItem implements Command
{
public function __construct(
#[AggregateUuid] public string $cartUuid,
public string $cartItemUuid,
public Product $product,
public int $amount,
) {
}
}
The #[HandledBy] attribute takes any invokable class. If you use an aggregate root class, the #[AggregateUuid] property is also required in order to map a command to an aggregate root.
If a command is handled by an aggregate root, you can simply add a method on that aggregate root which takes the command as an argument, and the rest will be handled for you:
class CartAggregateRoot extends AggregateRoot
{
public function addItem(
AddCartItem $addCartItem
): self {
}
}
Also note that these commands can be mapped to aggregate partials, this is especially useful when you don't want to provide a manual mapping of public methods between the aggregate root and its partials.
class CartItems extends AggregatePartial
{
public function addItem(
AddCartItem $addCartItem
): self {
}
}
Finally, a command is dispatched on the CommandBus, which is registered in Laravel's container, so you can inject is wherever needed:
class CartController
{
public function addCartItem(
Request $request,
CommandBus $commandBus
): void {
$commandBus->dispatch(new AddCartItem(
cartUuid: ,
cartItemUuid: ,
product: ,
amount: ,
));
}
}
##Want to know more?
Commands can be a very useful tool in complex applications. Our course, Event Sourcing in Laravel covers them in depth: