Error during compilation, Incompatible argument type: Required type: \Magento\Framework\DB\Adapter\AdapterInterface.

We can be resolved Compile time error by below way, The error looks like when running compilation command,

Incompatible argument type: Required type: \Magento\Framework\DB\Adapter\AdapterInterface. Actual type: string; File:
Error during compilation


From Magento 2.2.* version we need to pass full class name in__construct()  instead of $connection = null as di argument in Collection.php file.

Replace, $connection = null argument with \Magento\Framework\DB\Adapter\AdapterInterface $connection = null  in __construct() parameter.

Run again command,
php bin/magento setup:di:compile
an error will be gone.

How to get Value from Store Configuration by Scope in Magento 2?

To Fetch the System Store Configuration Values by Scope level, Store or Website, You need to use ScopeConfigInterface with getValue() method.

We can get the Core config data table value programmatically using the given way,

public function __construct(
    \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
    \Magento\Store\Model\StoreManagerInterface $storeManager
) {
    $this->scopeConfig = $scopeConfig;
    $this->storeManager = $storeManager;

Now call in a function,

public function getConfigValue() {
    return $this->scopeConfig->getValue("sectionId/groupId/fieldId",

First Argument sectionId/groupId/fieldId is from your etc/adminhtml/system.xml file.

The second Argument will be the Scope Value.

Third Argument will be scopeCode. It may be int, string or null value.

Demo system.xml to illustrate the example,

<?xml version="1.0"?>
<config xmlns:xsi="" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
        <section id="test" translate="label" type="text" sortOrder="310" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Test Settings</label>
            <group id="origin" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="0">
                <label>Main label</label>
                <field id="postcode" translate="label" type="text" sortOrder="30" showInDefault="1" showInWebsite="1" showInStore="0" canRestore="1">
                    <label>Postal Code</label>

In our case test/origin/postcode is the key value for sectionId/groupId/fieldId.

How to create creditmemo for order item programmatically in magento 2?

We can create credit memo for the specific item based on below way in Magento 2. We need to pass some basic data to generate credit memo in Magento 2. Continue reading “How to create creditmemo for order item programmatically in magento 2?”