Why Magento 2.2.3 returns empty collection?

Question

I don't have any prior experience in this. I want to fetch the products from Database. I am trying from past few hours.But not working.

I am using following code.

protected $_productCollectionFactory;

public function __construct(
    \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,        
    array $data = []
)
{    
    $this->_productCollectionFactory = $productCollectionFactory;    
}

public function getProducts()
{
    $collection = $this->_productCollectionFactory->create();
    $collection->addAttributeToSelect('*');
    $collection->setPageSize(3); // fetching only 3 products
    return $collection;
}

I am getting following response.

Anything wrong with this code?

Even I also want to fetch the customer collection as well.

Also I want to know the difference between ProductCollectionFactory & product.

Also I tried below code.

 namespace Testmod\FetchDataApi\Api;


 interface CustomerRepositoryInterface
{

   /**
   * @param int|string $number
  * @return  \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory
  */
    public function getCustomerParchases();
}

And my class:

namespace Testmod\FetchDataApi\Model;
use Magento\Framework\View\Element\Template;

 class CustomerRepository extends Template
 {

public function __construct(
    \Magento\Framework\View\Element\Template\Context $context,
    \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,
    array $data = []
) {

    $this->_productCollectionFactory = $productCollectionFactory;
    parent::__construct($context, $data);
}



  public function getCustomerParchases()
  {
    $collection = $this->_productCollectionFactory->create();
      $collection->addAttributeToSelect('*');
    return $collection;

 }
}

Above code will return []. But collection->count(); returns product count wwhich is 5.

Answer 1

I think the good way to get product collection is following :

public function __construct(
        \Magento\Catalog\Model\Product $product
    )
{
    $this->product = $product;
}

public function getCollection()
{
    $collection = $this->product->create()->getCollection();
    return $collection;
}

And for customer collection you can try following code :

 public function __construct(
        ...
        \Magento\Customer\Model\ResourceModel\Customer\CollectionFactory $customerFactory
        ...
    ) {
        ...
        $this->_customerFactory = $customerFactory;
        ...
    }

    public function getCustomerCollection()
    {   
        //Get customer collection
        return $this->_customerFactory->create();
    }