Q:

Yii2 searchmodel related model

As you can see I've gridview (from model called umumiy).  And via id_nomi I'm showing nomi.rus (which means rus column from nomi model):

The issue here is I'm trying to make search from Nomi model via umumiy gridview.  I'm trying to get values (with nomi.rus) via ajax.  This is what I tried:
    $model = new UmumiyModel();
    $searchModel = new UmumiyModelSearch();

    if (Yii::$app->request->isAjax){
        $data = Yii::$app->request->post();
        $searchModel->nomi->rus = $data['dori_nomi']; // search input value
        $dataProvider = $searchModel->search(Yii::$app->request->queryParams);
        return $this->renderPartial('sotish', [
            'searchModel' => $searchModel,
            'dataProvider' => $dataProvider,
            'model' => $model,
        ]);
    }

What am I doing wrong??? 

A:

You can use a public member in NomiSearch model to store text value from "Id Nomi" input field of gridview. 
So, in NomiSearch model:
class NomiSearch extends Nomi
{
    public $nomiText;

    public function rules()
    {
        return [
            // ...
            [['nomiText'], 'safe'],
        ];
    }

    public function search($params)
    {
        $query = Nomi::find();

        // add conditions that should always apply here

        $dataProvider = new ActiveDataProvider([
            'query' => $query,
        ]);

        $this->load($params);

        if (! $this->validate()) {
            // uncomment the following line if you do not want to return any records when validation fails
            // $query->where('0=1');
            return $dataProvider;
        }

        // grid filtering conditions
        $query->andFilterWhere([
        ]);

        if($this->nomiText!=null)
        {
            $query->andWhere(['IN', 'id_nomi', (new \yii\db\Query())->select('id')->from('nomi')->where(['like', 'nomi', $this->nomiText])]);
        }   

        return $dataProvider;
    }

}

Finally, in index view:
GridView::widget([
        'dataProvider' => $dataProvider,
        'filterModel' => $searchModel,
        'columns' => [
            [
                'label' => 'Id Nomi',
                'attribute' => 'nomiText',
                'value' => function($data) {
                    return $data->nomi->rus;
                },

            ],

