yii2里的hasOne怎么搞？

<?php
namespace frontend\models;
use yii\db\ActiveRecord;
use frontend\models\User;
class Article extends ActiveRecord
{
	public function getUserinfo()
	{
		return $this->hasOne(User::className(),['aid'=>'id']);
	}
}

<?php
namespace frontend\controllers;
use frontend\models\Article;
use frontend\models\User;
class IndexController extends \yii\web\Controller
{
	
	public function actionIndex()
	{
		$article=Article::findOne(['id'=>2]);
		var_dump($article->userinfo);
}}