Magento 2 – Proper Use of Helpers

best practicehelpermagento-2.1magento2template

I'm starting to see more and more people declaring helpers classes in order to be able to use the following in the template files:

$this->helper('Path/To/Helper/Class')->customMethod();

This kind of code lets people avoid the do not use the object manager directly restriction but I tend to see code that should be block code in those helpers.

So here are my questions:

what should one write in the helper classes ?
in which cases is it relevant to use helper methods in the templates?

Best Answer

Don't.
This is like using ObjectManager::getInstance()->create() in a template!
Use a custom Block that receives the helper as a constructor dependency instead, and add a proxy method that calls the helper method.

In the template:

$block->customMethod()

In the block:

public function __construct(Path/To/Helper/Class $helperClass, ...other dependencies...)
{
    $this->helper = $helperClass;
    // ...other assignments and call to parent::__construct()
}

public function customMethod()
{
    return $this->helper->customMethod();
}

In OOP principle speak this avoids violating the "Law of Demeter". It encapsulates the business logic in the block instead of the template. As a side effect it also makes the logic more testable as the logic is moved into the block.

Regarding what logic put into the helper classes, I find that in Magento 2 helpers mostly make sense for services, like something that is not a model, but contains reusable code, for example price formatting (which is contained in the core, but I can't think of a better example right now).

Related Solutions

Magento – Correct way of getting helper in template of custom block

The way to inject a helper into the Template model via DI (Dependency Injection) is to:

Extend the Magento\Framework\View\Element\Template block with your own (eg: class MyBlock extends \Magento\Framework\View\Element\Template)

Then in the MyBlock constructor, inject your Helper:

<?php
/**
 * @var \Magento\Search\Helper\Data $helper
 */
protected $helper;

public function __construct(
  \Magento\Framework\View\Element\Template\Context $context,
  \Magento\Search\Helper\Data $helper,
  array $data = []
) {
    $this->helper = $helper;
    parent::__construct($context, $data);
}

Then add a getter method to MyBlock:

<?php
function getDataHelper() {
    return $this->helper;
}

Define your block to use the new MyBlock you created (instead of Template):

<block class="Your\ModuleBlocks\MyBlock" 
  name="top.search" 
  as="topSearch" 
  template="Magento_Search::form.mini.phtml" 
 />

Then in your block .pthml template you can access the helper this way:
```
<?php $block->getDataHelper() ?>
```

It's certainly easier to just call $this->helper() in the .phtml template.

As for part 2 of your question, Magento\Framework\View\Element\Template is the $block object in your .phtml template, and you are correct: it does not have the helper() method.

However, the $this object in a .phtml template is the Magento\Framework\View\TemplateEngine\Php object, which does have that method (as noted in another answer).

(Using this helper() method requires that your helper extend the Magento\Framework\App\Helper\AbstractHelper class, it should be noted.)

Magento2 Best Practices – Using ObjectManager Directly

You should not use the ObjectManager directly!

Exception from the rule are:

in static magic methods like __wakeup, serialize, etc
in case you should make backward compatibility of constructor
in global scope, like in fixtures of integration test.
in class that needs only for creation of object like factory, proxy , etc

Best Answer

Related Solutions

Magento – Correct way of getting helper in template of custom block

Magento2 Best Practices – Using ObjectManager Directly

Related Topic