Magento 2 - How to know all valid attributes to use in addAttributeToSelect?

Question

I often see code like this where the developer just inserts * into addAttributeToSelect("*") instead of selecting only the necessary attributes.

public function toOptionArray()
{
    $optionArray = [];
    $arr = $this->collectionFactory->create()->addAttributeToSelect("*");

    foreach ($arr as $key => $value) {
        $optionArray[] = [
            'value' => $value->getId(),
            'label' => $value->getName(),
        ];
    }
    return $optionArray;
}

As you can see, only the attributes id and name are getting used, so the developer should configure addAttributeToSelect accordingly for better performance.

So I tried to improve the code by using this addAttributeToSelect("id, name"); but now the name is not available in the data anymore, because name does not seem to be the right column identifier.

How do I know all valid available attributes which I can use?

I looked up the database table catalog_category_entity and catalog_category_product but they do not even contain a column with name "id" and there is no information about the category name.

---

I also tried to output an element from $arr to see if it contains interesting information:

public function toOptionArray()
{
    $optionArray = [];
    $arr = $this->collectionFactory->create()->addAttributeToSelect("*");

    // Debug ------------------------------------------
    echo "<pre>";
        print_r($arr[0]);
    echo "</pre>";
    exit();
    // ------------------------------------------------

    foreach ($arr as $key => $value) {
        $optionArray[] = [
            'value' => $value->getId(),
            'label' => $value->getName(),
        ];
    }
    return $optionArray;
}

But I get

"Error: Cannot use object of type Magento\Catalog\Model\ResourceModel\Category\Collection as array in /home/x/y/app/code/Company/Shipping/Model/Source/Category.php:30"

... even though the same $arr is later used in the foreach with no problem, so the error makes no sense.

Answer 1

this function has a lot of abstraction/parsing and use of config files to decide on the fields to bring. Nowadays, we can also alter functions with plugins; meaning even if we come up with a rule to describe the fields to expect, essentially, they are liable to be changed by many parameters.

However, if you put the symbol *, you will see all the fields available in your query without any clever theory behind.

However, to retrieve a list of specific fields, you might want to use a list of fields as an array like my example below.

I put a few screenshots showing you on my PHPSTORM install how it looks and what does you can read:

$collection->addFieldToSelect('*'); gives the response below:

`$collection->addFieldToSelect(['small_image', 'name']);` gives the response below: