Series of fatal errors: missing get_default_import_options method, protected constructor, too few arguments passed to import method

[lgenter]

Hey team,

I'm attempting to implement a variation of this example add-on for RankMath fields. I've run into a series of fatal errors.

Error 1: On step 3, I get the same error about missing the get_default_import_options method mentioned in the previously closed issue. I added the method just to get around the error, and that worked, but obviously it would be good to have clearer documentation on this point as I haven't looked under the hood of the API.

Error 2: When running the import, it seems that the importer is trying to instantiate the add-on's class, but it can't because the constructor is protected. I'm sure I'm missing something here, but this leaves me confused. Here's the error:

PHP Fatal error: Uncaught Error: Call to protected WP_All_Import_RankMath_Add_On::__construct() from scope PMXI_Import_Record in {...plugins-path}/wp-all-import-pro/models/import/record.php:1650

Error 3: Not ideal, but I temporarily made the constructor public to test further, and got the following error:

PHP Fatal error: Uncaught ArgumentCountError: Too few arguments to function WP_All_Import_RankMath_Add_On::import(), 1 passed in {...plugins-path}/wp-all-import-pro/models/import/record.php on line 3170 and exactly 3 expected in {...plugins-path}/wp-all-import-rankmath-add-on/wp-all-import-rankmath-add-on.php:79

Would greatly appreciate input here or, if applicable, a fix in the example code to reflect any updates.

I'm including my plugin's code just in case it's a me problem. Running WP All Import Pro 4.9.8 on WP 6.7.1.

Thanks in advance!

if (!defined('ABSPATH')) {
    exit; // Exit if accessed directly
}

final class WP_All_Import_RankMath_Add_On {
    protected static $instance;
    protected $add_on;
    protected $addon_name = 'RankMath Add-On'; // Define the name of your add-on
    protected $addon_slug = 'wp_all_import_rankmath_add_on'; // Define a unique add-on slug

    // Singleton pattern to ensure only one instance of the add-on is loaded
    public static function get_instance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    // Constructor to add the init hook
    protected function __construct() {
        add_action('init', array($this, 'init'));
    }

    // Add static keyword and make it public
    public static function get_default_import_options() {
        return [
            'rankmath_title' => '',
            'rankmath_description' => '',
            'rankmath_focus_keyword' => '',
        ];
    }

    public function init() {
        // Check for required classes and display an admin notice if not found
        if (!class_exists('PMXI_Plugin') || !class_exists('PMXI_RapidAddon')) {
            add_action('admin_notices', function() {
                echo 'The RankMath Add-On requires WP All Import Pro to be installed and active.';
            });
            return;
        }

        // Include the 'is_plugin_active' function if it doesn't exist
        if (!function_exists('is_plugin_active')) {
            include_once(ABSPATH . 'wp-admin/includes/plugin.php');
        }

        // Check if the RankMath plugin is active
        if (!is_plugin_active('seo-by-rank-math/rank-math.php')) {
            add_action('admin_notices', function() {
                echo 'The RankMath Add-On requires the RankMath plugin to be installed and active.';
            });
            return;
        }

        // Initialize the add-on with its name and slug
        $this->add_on = new PMXI_RapidAddon($this->addon_name, $this->addon_slug);
        $this->wpai_setup_fields(); // Add fields to the add-on
        $this->add_on->set_import_function([$this, 'import']); // Set the import function
        $this->add_on->run(); // Run the add-on
    }

    // Define the fields for the import template
    public function wpai_setup_fields() {
        $this->add_on->add_field('rankmath_title', 'RankMath Meta Title', 'text');
        $this->add_on->add_field('rankmath_description', 'RankMath Meta Description', 'text');
        $this->add_on->add_field('rankmath_focus_keyword', 'RankMath Meta Keywords', 'text');
    }

    // Import function to handle the import of RankMath SEO data
    public function import($post_id, $data, $import_options) {
        $fields = ['rankmath_title', 'rankmath_description', 'rankmath_focus_keyword'];
        foreach ($fields as $field) {
            // Check if the field can be updated
            if (empty($data['ID']) || $this->add_on->can_update_meta($field, $import_options)) {
                // Update the custom field with the imported data
                update_post_meta($post_id, $field, $data[$field]);
            }
        }
    }
}

// Initialize the add-on
WP_All_Import_RankMath_Add_On::get_instance();