Why doesn't relation work in yii2?

Question

Yii

Tags.php

public function getArt() {
  $this->hasMany(Art::className(), ['id' => 'art_id'])
    ->viaTable('art_tag', ['tag_id' => 'id']);
}

controller

$tag = Tags::find()->joinWith('art')->where(['id' => $tag])->all();

As a result, the error

backend\models\Tags has no relation named "art".

Answer 1

return

public function getArt() {
  return $this->hasMany(Art::className(), ['id' => 'art_id'])
    ->viaTable('art_tag', ['tag_id' => 'id']);
}