Use extra_data

includes/class-wc-order-refund.php

@@ -21,17 +21,24 @@ class WC_Order_Refund extends WC_Abstract_Order {
 	 */
 	protected $data_store_name = 'order-refund';
 
+	/**
+	 * Stores product data.
+	 *
+	 * @var array
+	 */
+	protected $extra_data = array(
+		'amount'      => '',
+		'reason'      => '',
+		'refunded_by' => 0,
+	);
+
 	/**
 	 * Extend the abstract _data properties and then read the order object.
 	 *
 	 * @param int|object|WC_Order $read Order to init.
 	 */
 	 public function __construct( $read = 0 ) {
-		$this->data = array_merge( $this->data, array(
-			'amount'      => '',
-			'reason'      => '',
-			'refunded_by' => 0,
-		) );
+		$this->data = array_merge( $this->data, $this->extra_data );
 		parent::__construct( $read );
 	}