How to call a static function in add_action() inside another static function?

Question

In my plugin, I would like to load css only when the front-end current page is using one of my plugin shortcodes.

All my shortcodes are classes extending Shortcode class. Shortcode class helps me to automate the callback function.

Shortcode abstract class

namespace PluginFoo\Shortcodes;


abstract class Shortcode {

    public $tag;
    public $attrs;
    public $function;

    public function __construct($tag) {
        $this->attrs = array();
        $this->tag = $tag;
        $this->function = static::className().'::getCallBack';

        add_shortcode( $this->tag, $this->function );

    }

    abstract public static function className();

    abstract public static function getCallBack( $attrs ); 
}

FooShortcode class

namespace PluginFoo\Shortcodes;

class FooShortcode extends Shortcode {

    public static function getCallBack( $attrs = null ){

        add_action('wp_enqueue_scripts', array( __CLASS__, 'set_bootstrap' ) ); // <-- Here - function set_bootstrap not called !

        $output = '';

        ob_start();

        //HTML Template
         include_once 'shortcode-view.php';

        $output .= ob_get_contents();
        ob_end_clean();

        return $output;

    }

    public static function set_bootstrap() {
         wp_enqueue_style( 'bootstrapstyle', PLUGIN_DIR_URL . 'css/bootstrap.min.css' );
    }

    public static function className(){
        return __CLASS__;
    }
}

How can I call correcty the static function set_bootstrap() in add_action() inside an another static function ?

Answer 1

If your class is called statically you need to use get_called_class() like this:

add_action('wp_enqueue_scripts', array( get_called_class(), 'set_bootstrap' ) );

since $this is not available. This also works if the class is extended.

Answer 2

you can use classname::class for example:

add_shortcodes(callback::class, 'callbackmethod');