public function findDefaultCombinationAndUndefault()
    {
        if (!empty($this->id)) {
            $defaultProductCombinations = Combination::find()
                ->where(['product_id' => $this->product_id, 'default' => true])
                ->andWhere(['!=', 'id', $this->id])
                ->all();
        } else {
            $defaultProductCombinations = Combination::find()
                ->where(['product_id' => $this->product_id, 'default' => true])
                ->all();
        }

        if (!empty($defaultProductCombinations)) {
            foreach ($defaultProductCombinations as $defaultProductCombination) {
                $defaultProductCombination->default = 0;
                if ($defaultProductCombination->validate()) $defaultProductCombination->save();
            }

        }
    }