Catching exceptions and converting them to Symfony form errors

[webdevilopers]

If anywhere in your application e.g. in your Handler or DomainModel an Exception / DomainException is thrown you can catch and convert the message to use it in your Symfony form:

        $fooCommand = FooCommand::fromBar($bar);

        $form = $this->createForm(FooForm::class, $fooCommand);
        $form->handleRequest($this->getRequest());

        if ($form->isValid()) {
            $fooHandler = $this->get('acme.handler.foo');
            try {
                $fooHandler->handle($fooCommand);

                return $this->redirectToRoute('acme_foo_list');
            } catch (\Exception $e) {
                $form->addError(new FormError($e->getMessage()));
            }
        }

And then inside your TWIG template:

{{ form_errors(form) }}

[webdevilopers]

Normally we add value objects and asserts to our commands. So we thought about extending the try-catch-block to catch the exceptions:

• https://gist.github.com/webdevilopers/e2263debd573c90b51ab18702c3db4c9

But now we are thinking of moving the value objects to the "Handler": https://github.com/webdevilopers/php-ddd/issues/14

In that case we no longer would have to extend and keep it the original way - see initial comment.

[webdevilopers]

We decided to make our Command DTOs (aka Symfony Form data classes) using primitives only again. The creation of value objects was moved to the Command Handler. Every value object throws a specific Domain Exception if they cannot be created or violate a business rule.

Now we can use a single try-catch block to catch the exceptions and transform them into a Symfony Form error.

This example features the @prooph service-bus. The actual Domain Exception can be accessed by getting the previous exception:

        $form->handleRequest($this->getRequest());

        if ($form->isValid()) {
            try {
                $this->get('prooph_service_bus.acme_command_bus')->dispatch($command);
            } catch (\Exception $busException) {
                switch (get_class($busException->getPrevious()))
                {
                    case InnerWidthIsOutOfRangeException::class:
                        $form->get('window')->addError(new FormError('...'));
                        break;
                }
            }
        }

Is there a better way to get and handle the domain exceptions @prolic @codeliner?

[prolic]

The service bus will throw its own exceptions. If you don't like this behavior and want it to throw your custom exceptions directly instead, attach a listener to finalize event on the bus and replace the exception with the previous one.