Magento 2.1 Custom module relationship - magento

Question

I developed few custom modules for my Magento 2.1 store for smart manegmant of content in some of the CMS pages.
I used this tutorial https://www.ashsmith.io/magento2/module-from-scratch-introduction/ and this example https://github.com/ashsmith/magento2-blog-module-tutorial in order to do it.
Now, I have on page with list of FAQ, but each FAQ is belongs to FAQ Category (Not the Catalog Category).
So there is two custom modules here (FAQ Category and FAQ Question).
The FAQ Category only have Title field.
The FAQ Question have Title field, Answer (text editor) field, and FAQ Question dropdown (select box with list of all availble FAQ categories)
I don't know how to achive this.
What is the right way to do it? Especially the admin part.

Answer 1

I assume you want to join fields. You cannot do this by using virtual type in di.xml, so you need to follow these steps and update your files
#File etc/di.xml
<type name="Magento\Framework\View\Element\UiComponent\DataProvider\CollectionFactory">
<arguments>
<argument name="collections" xsi:type="array">
<item name="namespace_modulename_listing_data_source" xsi:type="string">Namespace\Modulename\Model\Resource\Modulename\Grid\Collection</item>
</argument>
</arguments>
</type>
<type name="Namespace\Modulename\Model\Resource\Modulename\Grid\Collection">
<arguments>
<argument name="mainTable" xsi:type="string">tablename</argument>
<argument name="eventPrefix" xsi:type="string">namespace_modulename_grid_collection</argument>
<argument name="eventObject" xsi:type="string">namespace_grid_collection</argument>
<argument name="resourceModel" xsi:type="string">Namespace\Modulename\Model\Resource\Modulename</argument>
</arguments>
</type>
In Your Resource Model File Model/Resource/Modulename/Collection.php
<?php
namespace Namespace\Modulename\Model\Resource\Modulename;
use Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection;
class Collection extends AbstractCollection
{
/**
* Define model & resource model
*/
const YOUR_TABLE = 'tablename';
public function __construct(
\Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
\Psr\Log\LoggerInterface $logger,
\Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
\Magento\Framework\Event\ManagerInterface $eventManager,
\Magento\Store\Model\StoreManagerInterface $storeManager,
\Magento\Framework\DB\Adapter\AdapterInterface $connection = null,
\Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
) {
$this->_init(
'Namespace\Modulename\Model\Modulename',
'Namespace\Modulename\Model\Resource\Modulename'
);
parent::__construct(
$entityFactory, $logger, $fetchStrategy, $eventManager, $connection,
$resource
);
$this->storeManager = $storeManager;
}
protected function _initSelect()
{
parent::_initSelect();
$this->getSelect()->joinLeft(
['join_table' => $this->getTable('tablename')],
'main_table.columnname = join_table.column_name',
'*'
);
}
}
?>
Now your Model/Resource/ModuleName/Grid/Collection.php
<?php
namespace Namespace\Modulename\Model\Resource\Modulename\Grid;
use Magento\Framework\Api\Search\SearchResultInterface;
use Magento\Framework\Search\AggregationInterface;
use Namespace\Modulename\Model\Resource\Modulename\Collection as ModulenameCollection;
/**
* Class Collection
* Collection for displaying grid
*/
class Collection extends ModulenameCollection implements SearchResultInterface
{
/**
* Resource initialization
* #return $this
*/
public function __construct(
\Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
\Psr\Log\LoggerInterface $logger,
\Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
\Magento\Framework\Event\ManagerInterface $eventManager,
\Magento\Store\Model\StoreManagerInterface $storeManager,
$mainTable,
$eventPrefix,
$eventObject,
$resourceModel,
$model = 'Magento\Framework\View\Element\UiComponent\DataProvider\Document',
$connection = null,
\Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
) {
parent::__construct(
$entityFactory,
$logger,
$fetchStrategy,
$eventManager,
$storeManager,
$connection,
$resource
);
$this->_eventPrefix = $eventPrefix;
$this->_eventObject = $eventObject;
$this->_init($model, $resourceModel);
$this->setMainTable($mainTable);
}
/**
* #return AggregationInterface
*/
public function getAggregations()
{
return $this->aggregations;
}
/**
* #param AggregationInterface $aggregations
*
* #return $this
*/
public function setAggregations($aggregations)
{
$this->aggregations = $aggregations;
}
/**
* Get search criteria.
*
* #return \Magento\Framework\Api\SearchCriteriaInterface|null
*/
public function getSearchCriteria()
{
return null;
}
/**
* Set search criteria.
*
* #param \Magento\Framework\Api\SearchCriteriaInterface $searchCriteria
*
* #return $this
* #SuppressWarnings(PHPMD.UnusedFormalParameter)
*/
public function setSearchCriteria(
\Magento\Framework\Api\SearchCriteriaInterface $searchCriteria = null
) {
return $this;
}
/**
* Get total count.
*
* #return int
*/
public function getTotalCount()
{
return $this->getSize();
}
/**
* Set total count.
*
* #param int $totalCount
*
* #return $this
* #SuppressWarnings(PHPMD.UnusedFormalParameter)
*/
public function setTotalCount($totalCount)
{
return $this;
}
/**
* Set items list.
*
* #param \Magento\Framework\Api\ExtensibleDataInterface[] $items
*
* #return $this
* #SuppressWarnings(PHPMD.UnusedFormalParameter)
*/
public function setItems(array $items = null)
{
return $this;
}
}
?>
Now you can use the join table columns any where in your grid and when you call collection.