Is dependency injection possible for plugins?

Question

I'm trying to make a plugin to extend the \Magento\SalesRule\Model\Validator

Which works like a charm, but the problem is I need to make use of Magento\SalesRule\Model\RuleFactory

I've tried making a __constructor in the plugin class and adding the RuleFactory there through dependency injection as described in het Magento 2 Developer Guide which looked like this:

The entire "Validator" plugin class now looks like this:

class Validator{
    /**
     * @var \Magento\SalesRule\Model\RuleFactory
     */
    private $ruleFactory;

    /**
    * @param \Magento\SalesRule\Model\RuleFactory $ruleFactory
     */
    public function __constructor(\Magento\SalesRule\Model\RuleFactory $ruleFactory){
        $this->ruleFactory = $ruleFactory;
        error_log('validator constructed');
    }

    public function aroundInit(\Magento\SalesRule\Model\Validator $subject, $procede, $websiteId, $customerGroupId, $couponCode){
        //custom before code
        $return = $proceed($websiteId, $customerGroupId, $couponCode);
        //custom after code
        return $return;
    }
}

but this would just return null for $this->ruleFactory at all times.

the di.xml document contains the following:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <type name="\Magento\SalesRule\Model\Validator">
        <plugin name="ValidatorPlugin" type="\MAS\CouponAttempt\Model\SalesRule\Validator" sortOrder="1" disabled="false"/>
    </type>
    <type name="\MAS\CouponAttempt\Model\SalesRule\Validator">
        <arguments>
            <argument name="ruleFactoryInjection" xsi:type="object">Magento\SalesRule\Model\RuleFactory</argument>
        </arguments>
    </type>
</config>

Interestingly enough I found that in the generated Interceptor.php file the constructor is actually made. But it is never called, can anybody tell me why this could be?

Answer 1

I decided to go with the less clean solution and just used a static instance of the objectmanager and got the rule factory through that

Answer 2

Late answer but you need to change __constructor to __construct and it will work perfectly well. Don't use static ObjectManager if possible. You should always use DI instead.

Answer 3

Yes, it is supported. Looks like in your sample function keyword is missing, try:

public function __constructor(\Magento\SalesRule\Model\RuleFactory $ruleFactory){
    $this->ruleFactory = $ruleFactory;
}