/**
  * @return \yii\db\ActiveQuery
  */
 public function getProduct()
 {
     return $this->hasOne(Product::className(), ['id' => 'product_id']);
 }
 /**
  * @return \yii\db\ActiveQuery
  */
 public function getProducts()
 {
     return $this->hasMany(Product::className(), ['user_id' => 'id']);
 }
 public function getProduct()
 {
     //同样第一个参数指定关联的子表模型类名
     return $this->hasOne(Product::className(), ['id' => 'productId']);
 }