Magento 2 Plugins / Interceptors accessing and modifying $this object - plugins

Question

I have a plugin that i want to modify functionality of a method within specific class in Magento 2 however am not quite sure on how to access the original object and return the modified data.
Original Method
protected function _initTotals()
{
$source = $this->getSource();
$this->_totals = [];
$this->_totals['subtotal'] = new \Magento\Framework\DataObject(
['code' => 'subtotal', 'value' => $source->getSubtotal(), 'label' => __('Subtotal')]
);
/**
* Add shipping
*/
if (!$source->getIsVirtual() && ((double)$source->getShippingAmount() || $source->getShippingDescription())) {
$this->_totals['shipping'] = new \Magento\Framework\DataObject(
[
'code' => 'shipping',
'field' => 'shipping_amount',
'value' => $this->getSource()->getShippingAmount(),
'label' => __('Shipping & Handling'),
]
);
}
/**
* Add discount
*/
if ((double)$this->getSource()->getDiscountAmount()) {
if ($this->getSource()->getDiscountDescription()) {
$discountLabel = __('Discount (%1)', $source->getDiscountDescription());
} else {
$discountLabel = __('Discount');
}
$this->_totals['discount'] = new \Magento\Framework\DataObject(
[
'code' => 'discount',
'field' => 'discount_amount',
'value' => $source->getDiscountAmount(),
'label' => $discountLabel,
]
);
}
$this->_totals['grand_total'] = new \Magento\Framework\DataObject(
[
'code' => 'grand_total',
'field' => 'grand_total',
'strong' => true,
'value' => $source->getGrandTotal(),
'label' => __('Grand Total'),
]
);
/**
* Base grandtotal
*/
if ($this->getOrder()->isCurrencyDifferent()) {
$this->_totals['base_grandtotal'] = new \Magento\Framework\DataObject(
[
'code' => 'base_grandtotal',
'value' => $this->getOrder()->formatBasePrice($source->getBaseGrandTotal()),
'label' => __('Grand Total to be Charged'),
'is_formated' => true,
]
);
}
return $this;
}
This i have set to have a plugin to modify functionality of method above with di.xml:
<type name="Magento\Sales\Block\Order\Totals">
<plugin disabled="false" name="Harrigo_EverDiscountLabel_Plugin_Magento_Sales_Block_Order_Totals" sortOrder="10" type="Harrigo\EverDiscountLabel\Plugin\Magento\Sales\Block\Order\Totals"/>
</type>
Plugin
class Totals
{
public function after_initTotals(
\Magento\Sales\Block\Order\Totals $subject,
$result
) {
if ((double)$subject->getSource()->getDiscountAmount() != 0 OR $subject->getSource()->getDiscountDescription() != null) {
if ($subject->getSource()->getDiscountDescription()) {
$discountLabel = __('Offer (%1)', $source->getDiscountDescription());
} else {
$discountLabel = __('Offer');
}
$subject->_totals['discount'] = new \Magento\Framework\DataObject(
[
'code' => 'discount',
'field' => 'discount_amount',
'value' => $source->getDiscountAmount(),
'label' => $discountLabel,
]
);
}
return $subject;
}
}
Have used $subject instead of $this within the plugin, this does not work for me however. How do I access the $this object within the plugin to add / overwrite $this->_totals['discount'] and return the updated $this object from within the plugin. I have it working fine with a standard preference but would rather use a plugin if possible.

Answer 1

I think you should check this before implementing above code.
http://devdocs.magento.com/guides/v2.0/extension-dev-guide/plugins.html
As per devdocs for Magento2 protected functions can not be intercepted so We can not use plugins for that.
May be that is causing issue in your case.
Hope this helps!