add_action( 'init', 'register_shortcodes');

add_shortcode( 'recent-posts', 'recent_posts_function' );

/**
   * Register all of the hooks related to the admin area functionality
   * of the plugin
   */

     private function define_admin_hooks() {

     $plugin_admin = new instance( $this->get_plugin_name(), $this->get_version() );

     $this->loader->add_action( 'init', $plugin_admin, 'register_shortcodes');
}

public function register_shortcodes(){

        add_shortcode('recent-posts', array($this, 'recent_posts_function'));

    }