Unable to plug in to the constructor (__construct method) but there is no such limitation in the documentation

[dmitrii-fediuk]

http://devdocs.magento.com/guides/v2.0/extension-dev-guide/plugins.html#plugin-limit
A similar issue #2265

[davidalger]

@dfediuk this is intrinsic to how PHP / OOP works. since the __construct method is called when the object is instantiated, it's simply not possible to intercept the call. The documentation should not contain a list of detailed scenarios which are not possible due to how OOP works. I'm closing this as a non-issue.

@xcomSteveJohnson feel free to chime in here if you wish

[dmitrii-fediuk]

Actually, it IS intercepted, for example:

<?php
namespace Magento\Authorization\Model\Role;

/**
 * Interceptor class for @see \Magento\Authorization\Model\Role
 */
class Interceptor extends \Magento\Authorization\Model\Role implements \Magento\Framework\Interception\InterceptorInterface
{
    use \Magento\Framework\Interception\Interceptor;

    public function __construct(\Magento\Framework\Model\Context $context, \Magento\Framework\Registry $registry, \Magento\Authorization\Model\ResourceModel\Role $resource, \Magento\Authorization\Model\ResourceModel\Role\Collection $resourceCollection, array $data = array())
    {
        $this->___init();
        parent::__construct($context, $registry, $resource, $resourceCollection, $data);
    }

    /**
     * {@inheritdoc}
     */
    public function update()
    {
        $pluginInfo = $this->pluginList->getNext($this->subjectType, 'update');
        if (!$pluginInfo) {
            return parent::update();
        } else {
            return $this->___callPlugins('update', func_get_args(), $pluginInfo);
        }
    }
}

Why not to call plugins before and after calling the parent (real class) contructor from the interceptor constructor?

[davidalger]

@dfediuk Had the chance to look at this further… I must have been tired from living on conference sleep when I replied initially. You're right, it is intercepted! :) Question though, are you recommending the documentation be amended or suggesting there is a need to allow plugins to wrap the __construct methods? My initial reaction to it being needed is that perhaps what needs to be plugged into should really be factored out of the construct method, but I'd like to know for sure what you're suggesting here.

[dmitrii-fediuk]

Surely, it would great to have the possibility to plug in to the constructors.

[davidalger]

+@antonkril

[antonkril]

What would be a scenario for such plugin?

One scenario we discussed was to have implicit factories - objects that would be called to define list of constructor arguments dynamically. Is it the way you want to use it?

Generally plugins are there to Intercept public method calls. Technically, constructor is not an object method. It's static function, we do not intercept static functions. But if there are useful scenarios, we might add this feature.

[dmitrii-fediuk]

1. To modify an argument of a constructor (before plugin)
2. To do some additional initialization after constuctor have finished (after plugin).
3. To change a constructor's behavior (around plugin)
   All of them have a practical sense.

[davidalger]

The documentation page has been updated for accuracy of current functionality.