TYPO3: Keep forms filled after form submit - php

Question

I created an extension which allows the user to sign up via the frontend. I couldn't use working ones because the client requested special tasks.
This is the code which detects taken usernames.
public function createAction(\Vendor\Feregister\Domain\Model\FeUserX $newFeUserX)
{
$uname = $newFeUserX->getUsername();
$select_query = '*';
$from_table = 'fe_users';
$where_clause = 'username="'.$uname.'"';
$test = $GLOBALS['TYPO3_DB']->exec_SELECTquery($select_query, $from_table, $where_clause);
if ($GLOBALS['TYPO3_DB']->sql_num_rows($test)) {
$this->addFlashMessage('Username is already taken.', '', \TYPO3\CMS\Core\Messaging\AbstractMessage::ERROR);
$this->redirect('new');
} else {
// do stuff when the username isn't taken yet
}
}
But unfortunately and obivously, when redirecting back to the new action, the fields are empty again.
Is there a way to pass the arguments back to the new action and fill the forms?

Answer 1

Yes, and extbase has a standardized way to do this. It works as follows:
If an action is called, its parameters are validated, except if validation is switched off in the doc comments. If validation fails, the previous action (the one whose view contained the submitted form) is called again, with the same parameters.
You can use this as follows:
/**
* #param \Vendor\Feregister\Domain\Model\FeUserX $newFeUserX
* #ignorevalidation $newFeUserX
*/
public function newAction(\Vendor\Feregister\Domain\Model\FeUserX $newFeUserX = null)
{
$this->view->assign('user', $newFeUserX);
// View renders form with name="newFeUserX" and object="{user}",
// action="create", fields use the property-attribute to fill
// in values and field names.
}
/**
* #param \Vendor\Feregister\Domain\Model\FeUserX $newFeUserX
* #validate $newFeUserX \Vendor\Feregister\Validator\UsernameDoesNotExistValidator
*/
public function createAction(\Vendor\Feregister\Domain\Model\FeUserX $newFeUserX)
{
// Do something with the user - you can be sure the username
// is not yet taken
}
The class \Vendor\Feregister\Validator\UsernameDoesNotExistValidator is a custom validator that implements the ValidatorInterface, or extends AbstractValidator. It should basically do the validation you are doing in your createAction (maybe using a repository instead of $GLOBALS['TYPO3_DB']). A validator returns errors in a standard way, making it easier to show nice error messages and localize them.
If the validation fails, extbase will try to forward to the action that rendered the form, in this case the new-action. In this case, it will work, because of the #ignorevalidation annotation on the new-action.
In addition, information about validation errors are available in the view, you can render them using the ViewHelper f:form.validationResults.