How to properly use relationships in Yii2?

Question

Yii

When generating the Payments model via Gii, the related tables were displayed only in the rules.
Function

public function getStates()
    {
        return $this->hasOne(PaymentStates::className(), ['id' => 'state']);
    }

added manually. Based on this model, I generated PaymentsSearch, where in the search function I added

$query->joinWith([
         'states' => function ($q2) {
           $q2->select(['name']);
         }

. Next, search is called in the controller and rendered

return $this->render('list', [
            'searchModel' => $searchModel,
            'dataProvider' => $dataProvider,
        ]);

List.php uses GridView, where I added a column to columns

[
          'attribute' => 'states.name',
          'format' => 'raw',
          'label' => 'Статус платежа',
          'value' => function (Payments $p) {
            switch ($p->state) {
              case 1 : $class = 'fa fa-question'; break;
              case 2 : $class = 'fa fa-times'; break;
              case 3 : $class = 'fa fa-check'; break;
            }
            return Html::tag('div',Html::tag('span','', ['class'=>$class])
                      . ' ' . $p->states->name);
          }
        ]

And here in the line $p->states->name the error Trying to get property of non-object is generated. What is the correct way to write the code so that $p->states returns a PaymentStates object?
The strangest thing is that this code worked, but I changed something (it seems that I just added fields to the table and regenerated Payments and PaymentsSearch). And now I can't figure out why it stopped working and how to use relationships in Yii2 at all.
There is also a connection with the User class, which in the same provider displays the necessary data correctly and the code there is almost the same

Answer 1

The getStates link returns null, the link does not mean that you have a state for each Payment. Check this point and make a check, either in code:

$state = ($p->states)?$p->states->name:'не определено';
return Html::tag('div',Html::tag('span','', ['class'=>$class]). ' ' . $state);

or in the model like so:

public function getStateName()
    {
        $name = 'хз';
        if($this->states)
            $name = $this->states->name;
        return $name;
    }

well, it's natural to use $model->stateName instead of $model->states->name

Answer 2

Instead of

$query->joinWith([
         'states' => function ($q2) {
           $q2->select(['name']);
         }

used

$query->with([
         'states'
       ]);

And everything began to display correctly. I don't know what the difference is between the two, but it definitely worked through joinWith before.