TYPO3 TCA make the 'default' value dynamic - typo3

Question

The title is rather self explanatory, but what i would like to have is a dynamic default value.
The idea behind it is to get the biggest number from a column in the database and then add one to the result. This result should be saved as the default value.
Lets take for example this code:
$GLOBALS['TCA'][$modelName]['columns']['autojobnumber'] = array(
'exclude' => true,
'label' => 'LLL:EXT:path/To/The/LLL:tx_extension_domain_model_job_autojobnumber',
'config' => [
'type' => 'input',
'size' => 10,
'eval' => 'trim,int',
'readOnly' =>1,
'default' => $result,
]
);
The SQL looks like this:
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tx_extension_domain_model_job');
$getBiggestNumber = $queryBuilder
->select('autojobnumber')
->from('tx_extension_domain_model_job')
->groupBy('autojobnumber')
->orderBy('autojobnumber', 'DESC')
->setMaxResults(1)
->execute()
->fetchColumn(0);
$result = $getBiggestNumber + 1;
So how can i do that "clean"?
I thought about processCmdmap_preProcess but i dont know how to pass the value to the coorisponding TCA field. Plus i do not get any results on my backend when i use the DebuggerUtility like i get them when i use processDatamap_afterAllOperations after saving the Object.
Can someone point me to the right direction?

Answer 1

I don't think it is supported to create a dynamic default value, see default property of input field.
What you can do however, is to create your own type (use this instead of type="input"). You can use the "user" type. (It might also be possible to create your own renderType for type="input", I never did this, but created custom renderTypes for type= "select").
You can look at the code of InputTextElement, extend that or create your own from scratch.
core code: InputTextElement
documentation for user type
more examples in FormEngine documentation
Example
(slightly modified, from documentation)
ext_localconf.php:
$GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['nodeRegistry'][<current timestamp>] = [
'nodeName' => 'customInputField',
'priority' => 40,
'class' => \T3docs\Examples\Form\Element\CustomInputElement::class,
];
CustomInputElement
<?php
declare(strict_types = 1);
namespace Myvendor\MyExtension\Backend\FormEngine\Element\CustomInputElement;
use TYPO3\CMS\Backend\Form\Element\AbstractFormElement;
// extend from AbstractFormElement
// alternatively, extend from existing Type and extend it.
class CustomInputElement extends AbstractFormElement
{
public function render():array
{
$resultArray = $this->initializeResultArray();
// add some HTML
$resultArray['html'] = 'something ...';
// ... see docs + core for more info what you can set here!
return $resultArray;
}
}