php - How to get the Variation ID in a Woocommerce product -

i'm trying in plugin i'm writing variation id of products. here's wrote:

class mass {      public function __construct()     {         add_action('woocommerce_product_after_variable_attributes',array($this,'thfo_mass'));       } public function thfo_mass()     {         $id = wc_product_variation::get_variation_id();         //$lenght = get_post_meta($id,'_length');         //$dimensions = wc_get_dimension(24750, 'cm');         var_dump($id);     } 

i error:

deprecated: non-static method wc_product_variation::get_variation_id() should not called statically, assuming $this incompatible context in path/to/plugins/thfo-raw-material-for-woocommerce/class/mass.php on line 19

notice: undefined property: mass::$variation_id in path/to/wp-content/plugins/woocommerce/includes/class-wc-product-variation.php on line 257 int(0)

try this.

 <?php      $product_obj = new wc_product_factory();     $product = $product_obj->get_product($product);                                  if ($product->product_type == 'variable'):         $children   = $product->get_children( $args = '', $output = object );          foreach ($children $key=>$value) {             $product_variatons = new wc_product_variation($value);             if ( $product_variatons->exists() && $product_variatons->variation_is_visible() ) {                 $variations[$value] = $product_variatons->get_variation_attributes();             }         }    endif;