Trying to get property of non-object in kartik expandrow in yii2 - yii2

Question

I'm trying to use kartik expandrow.
In the first level query in PartiesSearch Model is-
$query = (new Query())->select(['district'])->from('districts');
In the second level query in ExpartiesSearch Model is -
$query = (new Query())->select(['parties_district','parties_partyname'])->from('parties');
The code for expandrow in index.php is -
[
//['class' => 'yii\grid\SerialColumn'],
'class' => 'kartik\grid\ExpandRowColumn',
'value' => function($model, $key, $index, $column){
return GridView::ROW_COLLAPSED;
},
'detail' => function($model, $key, $index, $column){
$searchModel = new ExpartiesSearch();
$searchModel-> parties_district = $model-> district;
$dataProvider = $searchModel->search(Yii::$app->request->queryParams);
return Yii::$app->controller->renderPartial('_exparties', [
'searchModel' => $searchModel,
'dataProvider' => $dataProvider,
]);
},
],
I'm getting error -
Trying to get property of non-object
The highlighted error line is -
$searchModel-> parties_district = $model-> district;
The same piece of code works fine if I change the query in PartiesSearch Model to
$sql = 'select district from districts';
$query = Districts::findBySql($sql);
But, I have to write the query in that particular format (Derived from Query Builder) only. Please help.

Answer 1

In my test this:
$query = (new Query())->select(['district'])->from('districts');
will return you array of arrays. You need to use $model['district'] in this case.
[
//['class' => 'yii\grid\SerialColumn'],
'class' => 'kartik\grid\ExpandRowColumn',
'value' => function ($model, $key, $index, $column) {
return GridView::ROW_COLLAPSED;
},
'detail' => function ($model, $key, $index, $column) {
$searchModel = new ExpartiesSearch();
$searchModel->parties_district = $model['district'];
$dataProvider = $searchModel->search(Yii::$app->request->queryParams);
return Yii::$app->controller->renderPartial('_exparties', [
'searchModel' => $searchModel,
'dataProvider' => $dataProvider,
]);
},
Try to use xdebug to see what exactly in your $model