ZF2 Service Locator

Question

I'm quite new to zf2 and I'm experimenting with it. I have a view helper and I need it to access a table object. In my controller I can run:

$this->getServiceLocator();

But ideally I would run this inside my view helper. Unfortunately, I can't seem to access it from within my view helper. I tried passing it through the constructor, configuring a factory method in module.config.php, but when I try that, Zend will no longer pass a tablegateway object into one of my model objects created from a service factory method in the module's Module.php file. This seems to be because it no longer calls the factory method, and opts to run instantiate without any parameters.

I'm not certain I understand why the view factory methods would affect a different set of factory methods with different names.

Can anyone tell me what is wrong with what I'm doing? I can provide more details, but at this point I'm unclear on what details are actually important without supplying the entire codebase.

Thanks.

Answer 1

Crisp does provide a valid answer to your question, but I would suggest to take it one step further. The injection of the service locator makes your view helper tightly coupled to the framework and service locator pattern and vulnerable because every piece of code inside your application can modify every service in the service locator.

There are reasons to inject your dependency directly, so you only depend on your dependencies and you're not implementing this anti-pattern anymore. Let's assume your view helper depends on MyModule\Model\MyTable, then the constructor of your view helper would just look like this:

namespace MyModule;

use MyModule\Model\MyTable;
use Zend\View\Helper\AbstractHelper;

class MyViewHelper extends AbstractHelper
{
  protected $table;

  public function __construct(MyTable $table)
  {
    $this->table = $table;
  }
}

As you pointed out, you just inject your MyTable now:

namespace MyModule;

class Module
{
  public function getViewHelperConfig()
  {
    return array(
      'factories' => array(
        'MyViewHelper' => function($sm) {
          $sm = $sm->getServiceLocator(); // $sm was the view helper's locator
          $table = $sm->get('MyModule_MyTable');

          $helper = new MyModule\View\Helper\MyHelper($table);
          return $helper;
        }
      )
    );
  }
}

Note that inside a view helper factory your service manager is the view helper's service manager and not the "main" one where the table is registered (see also a blog post of I wrote earlier). The $sm->getServiceLocator() solves this for you.

I'm not certain I understand why the view factory methods would affect a different set of factory methods with different names.

It's not, so there is probably a bug in your code. If above does not work, please provide some more details on your service manager configuration so I can update my answer.

One of the great advantages of above approach is you make unit testing really easy for your view helper. You can mock the table gateway and focus on the complete behaviour of your view helper.

use MyModule\View\Helper\MyHelper;

public function testHelperusesTable
{
  $mock   = $this->getMock('MyModule\Model\MyTable');
  $helper = new MyHelper($mock);

  // Test your $helper now
}

Answer 2

You can inject the service locator into your view helper from the view helper config in Module.php

// Application/Module.php

public function getViewHelperConfig()
{
    return array(
        'factories' => array(
            'myViewHelper' => function ($serviceManager) {
                // Get the service locator 
                $serviceLocator = $serviceManager->getServiceLocator();
                // pass it to your helper 
                return new \Application\View\Helper\MyViewHelper($serviceLocator);
            }
        )
    );
}

In your view helper

<?php
namespace Application\View\Helper;

use Zend\View\Helper\AbstractHelper,
    Zend\ServiceManager\ServiceLocatorInterface as ServiceLocator;

class MyViewHelper extends AbstractHelper
{
    protected $serviceLocator;

    public function __construct(ServiceLocator $serviceLocator)
    {
        $this->serviceLocator = $serviceLocator;
    }
}

Answer 3

While working in Zend Framework,we often need custom helper,that make our work easy, In zf1 accessing database model from helper was easy,but i got stuck that how to access database model for any table in Custom View Helper, but as i was needing it i get around through the problem in unprofessional way by creatina new db adapter object in the view, which was never good way, but recently i came to know through very interesting way to access the database adapter in the view helper and there i have to execute any query on any table, it may be not so Zend F2 way, but very simple and short way to solve the issue.

Here is my Model Example...

<?php

namespace Application\Model;

use Zend\Db\TableGateway\TableGateway;

class SlideImageSubTable {

    protected $tableGateway;
    public $adapter;

    public function __construct(TableGateway $tableGateway) {
        $this->tableGateway = $tableGateway;
        $this->adapter = $this->tableGateway->getAdapter();
    }

    public function fetchAll() {
        $resultSet = $this->tableGateway->select();
        return $resultSet;
    }

    public function getSlideImageSub($id) {
        $id = (int) $id;
        $rowset = $this->tableGateway->select(array('id' => $id));
        $row = $rowset->current();
        if (!$row) {
            throw new \Exception("Could not find row $id");
        }
        return $row;
    }

    public function getImageMenu($id) {
        $id = (int) $id;
        $rowset = $this->tableGateway->select(array('slide_image_id' => $id));
        $rows = array_values(iterator_to_array($rowset));
        if (!$rows) {
            throw new \Exception("Could not find row $id");
        }
        return $rows;
    }

    public function saveSlideImageSub(SlideImageSub $slideImageSub) {
        $data = array(
            'slide_image_id' => $slideImageSub->slide_image_id,
            'title' => $slideImageSub->title,
            'description' => $slideImageSub->description
        );

        $id = (int) $slideImageSub->id;
        if ($id == 0) {
            $this->tableGateway->insert($data);
        } else {
            if ($this->getSlideImageSub($id)) {
                $this->tableGateway->update($data, array('id' => $id));
            } else {
                throw new \Exception('Form id does not exist');
            }
        }
    }

    public function deleteSlideImageSub($id) {
        $this->tableGateway->delete(array('id' => $id));
    }

}

Just look at the 'public $adapter' public variable. And in the constructor i am going to initialize it by calling $this->tableGateway->getAdapter(); method, getAdapter() is available thorugh gateway object.

Then in my controller action view, i have to assign it to any variable and pass that variable to view page. like this..

public function equitiesAction() {
        $image_id = $this->params('id');
        $result = $this->getTable('SlideImageSub')->getImageMenu($image_id);
        $adapter = $this->table->adapter;
        $view = new ViewModel(array(
                    'result' => $result,
                    'adapter' => $adapter,
                ));
        return $view;
    }

And in the view i pass the 'adapter' object to custom view like this..

<?php echo $this->GetMenuProducts( $this->adapter); ?>

Now in custom view i can use this database adapter object and create select query on any table.

Hope this will help someone, i look around for using database access in custom view helper but the configurations methods provided was not working for me.

Thanks

Answer 4

$this->getView()->getHelperPluginManager()->getServiceLocator();