/**
* @return \yii\db\ActiveQuery
*/
public function getActivities()
{
return $this->hasMany(Activity::className(), ['category_id' => 'id']);
}
public function getActivity()
{
//同样第一个参数指定关联的子表模型类名
//
return $this->hasOne(Activity::className(), ['id' => 'activity_id']);
}
/**
* @return \yii\db\ActiveQuery
*/
public function getActivity0()
{
return $this->hasOne(Activity::className(), ['id' => 'activity']);
}