hasOne relation is not working for me


I have a hasOne relation, which is not working for me, but I do not find why.

So, here the property calling:

var_dump($entity->activity) //which cause the above pasted error message.

But in the House AR model I defined the following hasOne relation:


 * // Properties.


 * @property Activity $activity


class House extends \yii\db\ActiveRecord




     * @return \yii\db\ActiveQuery


    public function getActivity()


        return $this->hasOne(Activity::className(), ['entity' => Activity::ENTITY_HOUSE, 'entity_id' => 'id']);


The other hasOne relations work fine, but not this one.