Module development and code questions

I have created a custom form and it works.
I need to create another module by clicking on install this error returns me and I don't know what to do to solve the problem. I tried to delete and reinstall it but nothing to do

ReflectionException: Class \Drupal\hello\HelloController does not exist in ReflectionMethod->__construct() (line 136 of core\lib\Drupal\Core\Entity\EntityResolverManager.php).

Hi all,

I'm working on an external script using user database and rights management from Drupal 7. It was working fine till some update on the server (unfortunately I'm not able to get exact info about updates from the provider, or maybe it is casused by some change in Drupal I dont remeber). 

At the beginning of the srcipt I'm loading drupal core using this:

I am trying to add a new column to a table and I added the column using hook_update_N() in the module.install file:

Hello all,

I am trying to patch a submodule: jsonapi_defaults installed with jsonapi_extras (modules/jsonapi_extras/jsonapi_defaults) using composer on Drupal 8.9.10.

I tried the following:

    "extra": {
         "patches": {
        "drupal/jsonapi_extras" : {
        "Configurable JSON:API Max Limit": "https://www.drupal.org/files/issues/2020-08-09/max-page-limit-configurable_2884292_17.patch"
         }
        },

But was not able to apply patch to the submodule.

Thanks in advance.

I use feeds to import data from csv file with eck entity processor and feeds module drupal 7, in fields of bundel i have entity reference field named nom candidat like in image bellow, but when i import data from csv file i need to create if note existe a new entity candidat in candidat entity type. In this case i have setup used feed entity reference and maping field "nom candidat" to according entity id, but when i upload to file it doesn't create candidat entity if not existe, how i can do that please 

Hello,

In my custom form I'am trying to get values from a nested taxonomy checkboxes field.

$form['test'] = [
'#type' => 'checkboxes',
'#title' => t('title'),
0 => array(
'#type' => 'checkboxes',
'#options' => array('1' => 'one'),
0 => array(
'#type' => 'checkboxes',
'#options' => array('2' => 'two'),
),
),
1 => array('#type' => 'checkboxes',
'#options' => array('3' => 'three'),
),
];