Symfony 3 - Define form as a service

Defining a form type as service does not imply passing the instance retrieved from to container to createForm. when doing this, the container is not involved as far as the form component is involved.

To use a form type registered as a service (with the form.type tag so that the form component knows about it), you just just reference it by its name (i.e. the fully qualified class name in Symfony 2.8+ and the type name in older versions) in createForm or in FormBuilder::add.This is exactly what you do for Symfony core types btw (text, choice and so on), which are registered as services.the code of your controller does not change at all when using the form type as a service rather than having a form type without dependency and registered implicitly on first usage.

This is what i did to inject a form as a service in Symfony 3 from my Symfony 2 Code.

In my service.yml i changed

issue.form:    class: Gutersohn\Bundle\CoreBundle\Form\IssueType    arguments: ['@service_container']    tags:        - { name: form.type, alias: issue }

to

issue.form:    class: Gutersohn\Bundle\CoreBundle\Form\IssueType    arguments: ['@service_container']    tags:        - { name: form.type }

In my controller i changed

$form = $this->container->get('form.factory')->create($this->container->get('issue.form'), $issue, [        "method" => "post",        "action" => $this->container->get('router')->generate("ticket_add")]);

to

$form = $this->container->get('form.factory')->create(IssueType::class, $issue, [        "method" => "post",        "action" => $this->container->get('router')->generate("ticket_add")]); 

In issue #17013 on GitHub, aliemre stated:

Adding form.type tag is enough in your service definition.

app.form.corporation_type:    class: App\CorporationBundle\Form\CorporationType    arguments: ["@doctrine.orm.entity_manager"]    tags:        - { name: form.type }

Controller should remain same:

$form = $this->createForm(CorporationType::class, $corporation);

I've tested and it works!