My custom Product back-office field displays and loads fine, but won't save

[TinoArts]

I've added a custom 'my_field' field to the back office of my Product, to the Quantities section. It should be a non-translateable basic integer field. This is what I did:

In the Database

ALTER TABLE ps_product ADD COLUMN my_field INT DEFAULT 0

 

In Product.php

public $my_field;

public static $definition = array(
        'table' => 'product',
        'primary' => 'id_product',
        'multilang' => true,
        'multilang_shop' => true,
        'fields' => array(
            /* Classic fields */
			...
            'my_field' => array('type' => self::TYPE_INT, 'validate' => 'isInt'),
			...

public function loadStockData() {
	...
	$this->my_field = Db::getInstance()->getValue('SELECT `my_field` FROM `ps_product` WHERE id_product = ' . $this->id);
	...
}

 

In \src\PrestaShopBundle\Form\Admin\Product\ProductQuantity.php (to the appropriate place)

->add(
  'my_field',
  FormType\NumberType::class,
  [
    'label' => $this->translator->trans('My custom field', [], 'Admin.Catalog.Feature'),
    'constraints' => [
      new Assert\NotBlank(),
      new Assert\Type(['type' => 'numeric']),
  	],
  ]
)

 

In AdminModelAdapter.php

private $multiShopKeys = array(
	...
	'my_field', // Not sure if this is necessary
	...
);

...

private $unmapKeys = array(
	...
	'my_field',
	...
);

...

private function mapStep3FormData(Product $product)
{
  return array(
    ...
    'my_field' => $product->my_field,
    ...
  );
}

 

Lastly I've added my field to the product and combinations twig templates.

Now the field displays just fine, exactly when I want it to be. It nicely fetches the value from the database (0 by default, or different number if I change it manually in the db), but the field won't save. I tried performing an update query in Products.php's update() method like this:

public function update($null_values = false)
{
  ...

  // Update my custom field column
  Db::getInstance()->update('product', array(
  	'my_field' => $this->my_field,
  ), 'id_product = ' . (int) $this->id);

  ...
}

But it does not work, since $this->my_field seems to be always zero.

What is the correct way to save my value? Thank you.

Edited July 13, 2020 by TinoArts (see edit history)