Module Config File: Resource Connection Definitions Explained

configurationdatabasemodule

I searched for that information quite a while but did not found any explanation.

Many examples and tutorials for custom modules with custom database tables suggest the following for the config.xml file of corresponding module:

<resources>
    <[modulename]_setup>
        <setup>
            <module>[NAMESPACE]_[MODULENAME]</module>
            <class>Mage_Eav_Model_Entity_Setup</class>
        </setup>
        <connection>
            <use>core_setup</use>
        </connection>
    </[modulename]_setup>
    <[modulename]_write>
        <connection>
            <use>core_write</use>
        </connection>
    </[modulename]_write>
    <[modulename]_read>
        <connection>
            <use>core_read</use>
        </connection>
    </[modulename]_read>
</resources>

So my questions are:

What are [modulename]_write and [modulename]_read for?
What is the connection definition in [modulename]_setup for?
What is <class>Mage_Eav_Model_Entity_Setup</class> for?

I ask this, because it works well with just

<resources>
    <[modulename]_setup>
        <setup>
            <module>[NAMESPACE]_[MODULENAME]</module>
        </setup>
    </[modulename]_setup>
</resources>

Best Answer

The <[modulename]_write> and <[modulename]_read> db resources are no longer required since Magento 1.4. Configuring them does no harm however, the core/resource class automatically falls back to the default_* set of db resources.
I guess most people still put them there because they follow old blog posts. The only valid reason would be if indeed a custom db connection would be configured, different from the default one, or to have your module support ancient Magento instances.

The <[modulename]_setup> resource is for using setup scripts with your module. The <class> node defines the PHP class that will execute the setup scripts found in sql/ or data/. If the <class> node is omitted, the default setup class Mage_Core_Model_Resource_Setup is used.

Related Solutions

Can’t Save Role Resource for Custom Module – Magento 1 Solution

The problem here is that your resource has to match the menu name. This is a convention in Magento and if you do not do this, then it will show, but you cannot save the values. This is a problem I faced often before.

Here is a simple example of how it should work:

<?xml version="1.0" ?>
<config>
    <menu>
        <mycustom_menu translate="title" module="YOUR_MODULE_NAME">
            <title>My Menu</title>
            <sort_order>100</sort_order>
            <children>
                <!-- children -->
                <subitem translate="title" module="YOUR_MODULE_NAME">
                    <title>Subitem</title>
                    <sort_order>10</sort_order>
                    <action>adminhtml/mycustom_controller/</action>
                </subitem>
            </children>
        </mycustom_menu>
    </menu>
    <acl>
        <resources>
            <admin>
                <children>
                    <mycustom_menu translate="title" module="YOUR_MODULE_NAME">
                        <title>My Menu</title>
                        <sort_order>300</sort_order>
                        <children>
                            <!-- children -->
                            <subitem translate="title" module="YOUR_MODULE_NAME">
                                <title>Subitem</title>
                                <sort_order>10</sort_order>
                            </subitem>
                        </children>
                    </mycustom_menu>
                </children>
            </admin>
        </resources>
    </acl>
</config>

EDIT: Also have a look here for a great tutorial of system configuration and ACL http://alanstorm.com/custom_magento_system_configuration

Magento – Magento ensure module config is loaded last

From what I am reading, the only way to do this is by the depends tag, even if you made your module name ZZZ... The module list is re-ordered after being fetched based on dependencies...

The function Mage_Core_Model_Config::_loadDeclaredModules scans the directory etc/modules and loads XML files located there. These files contain module declarations. Before loading their contents, the system arranges them into a specific order. The first file in this list is Mage_All.xml. The modules declared in this file comprise the essential core functionality of Magento. Next in line are the declaration files whose names begin with Mage_. The modules declared there are a part of the Magento core as well, but often depend on the modules from the Mage_All.xml file and thus must be loaded after those. The rest of the list are declarations of third party modules: community modules and your local extensions. Once the list is compiled, Magento fetches the files in the order they are listed and loads their contents into an object of type Mage_Core_Model_Config_Base – the application configuration object, which Magento queries whenever a configuration entry is requested. The loaded configuration must be ordered once more – this time according to module dependencies.

Best Answer

Related Solutions

Can’t Save Role Resource for Custom Module – Magento 1 Solution

Magento – Magento ensure module config is loaded last

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