Magento 2 Form Field Array (Advance system configuration option)

Question

Recently I worked on advance system config form field in Magento 2. I checked Braintree payment method for reference.

When I saved a value, it showing following error:

Something went wrong while saving this configuration: Notice: Array to string conversion in
E:\wamp\www\magento2\app\code\Magento\Config\Model\Resource\Config\Data.php on line 38

After print $object->getValue() array is printed with error:

and

(click screenshots to enlarge)

Answer 1

Add backend model for this config path. Something like

<backend_model>NameSpace\Module\Model\Backend\Config</backend_model>

And backend model class looks like

namespace NameSpace\Module\Model\Backend
class Config  extends \Magento\Framework\App\Config\Value
{
    public function beforeSave()
    {
        $data = $this->getValue();
        if (is_array($data)) {
            $this->setValue(implode(',', $data));
        }
    }
}

Answer 2

In Magento 2 serialize values are not directly saved in database it's using some encryption method to store serialize values. After some r & d I found these two methods in Magento 2 to convert serialize and store in db:

   protected function encodeArrayFieldValue(array $value)

and:

   protected function decodeArrayFieldValue(array $value)

Answer 3

You have to set a backend_model for your field in the xml. If you don't have any special needs you can use the ArraySerialized model:

<backend_model>Magento\Config\Model\Config\Backend\Serialized\ArraySerialized</backend_model>