How to add something to result of a method with a plugin

Question

How in magento I can add something using plugin to result of a method. Having this dummy class and trying to change bar() methods return:

class A
{

    public function foo($str)
    {
        return $str;
    }

    public function bar()
    {
        return $this->foo('Some msg!!!');
    }

}

Thank you.

Answer 1

Example: add a string to getName() of Product class.

You have to create app/code/vendorName/moduleName/etc/di.xml:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Catalog\Model\Product">
        <plugin name="plugin_name" type="VendorName\ModuleName\Plugin\Catalog\ProductAfter" />
    </type>
</config>

and app/code/VendorName/ModuleName/Plugin/Catalog/ProductAfter.php:

<?php

namespace VendorName\ModuleName\Plugin\Catalog;

class ProductAround
{
    public function afterGetName(\Magento\Catalog\Model\Product $product, $result)
    {
        return $result." string";
    }
}

The result is: the name of product + " string".