Create a new module in magento

When you need to add new functionality or want to edit existing magento class in both case you should create a new module. Suppose, you want to add “User Credit” system then you need to create a new UserCredit module in magento. And if you want to edit/update customer functionality  then you should follow magento override rules. To override existing Customer module you should create another new customer  module name M4U_Customer in local pool. In this case you need to use magento rewrite rules. When you go to add or edit something in magento,  each time you can be done as separate module or few methods can be combined in same module if they share functionality or could be used together.

Let’s create a module :

Module Declaration:
Create app/etc/modules/M4U_NewModule.xml and write below code

<?xml version="1.0"?>
<config>
         <modules>
<!-- declare CompanyName_NewModule module -->
           <M4U_NewModule>
<!-- this is an active module -->
                  <active>true</active>
<!-- this module will be located in app/code/local code pool -->
                  <codePool>local</codePool>
<!-- specify dependencies for correct module loading order -->
                  <depends>
                             <Mage_ExistingModule />
                  </depends>
<!-- declare module's version information for database updates -->
                  <version>0.1.0</version>
           </M4U_NewModule>
	</modules>
</config>

Here is example of create new M4U_customer module to override existing Mage_Customer module and M4U_Credit module to create new credit module.

<config>
    <modules>
        <M4U_Customer>
           <active>true</active>
           <codePool>local</codePool>
        </M4U_Customer>
        <M4U_Credit>
           <active>true</active>
           <codePool>local</codePool>
        </M4U_Credit>
    </modules>
</config>

Our new module will be called NewModule.

Replace all instances of ‘NewModule’ with name of your module and ‘newmodule’ with simplified code, that contains only alphanumeric characters and underscore.

To make this tutorial most concise, it’s implied that mentioned folders will be created when needed.

Module Configuration:

Create Model, Helper, coltrollers, Block, sql and etc folder under  app/code/local/M4U/NewModule/ and configure app/code/local/M4U/NewModule/etc/config.xml like below:

<?xml version="1.0"?>
   <config>
       <modules>
           <M4U_NewModule>
                 <version>0.1.0</version>
           </M4U_NewModule>
       </modules>

<!-- define Front end controller and template  -->
       <frontend>
<!-- define Front end controller  -->
           <routers>
               <newmodule>
                   <use>standard</use>
                   <args>
                          <module>M4U_NewModule</module>
                          <frontName>newmodule</frontName>
                   </args>
               </newmodule>
           </routers>
<!-- define Front end template xml -->
           <layout>
               <updates>
                    <newmodule>
                         <file>newmodule.xml</file>
                    </newmodule>
                </updates>
              </layout>
           </frontend>   

<!-- define blocks, models, helpers in global area -->
            <global>
               <models>
                  <newmodule>
                         <class>M4U_NewModule_Model</class>
                  </newmodule>
               </models>
               <blocks>
                  <newmodule>
                          <class>M4U_NewModule_Block</class>
                  </newmodule>
               </blocks>
               <helpers>
                  <newmodule>
                          <class>M4U_NewModule_Helper</class>
                  </newmodule>
               </helpers>

<!-- declare resource setup for new module -->
               <resources>
                    <newmodule_setup>
<!-- specify that this resource is a setup resource and used for upgrades -->
                       <setup>
<!-- which module to look for install/upgrade files in -->
                           <module>M4U_NewModule</module>
                       </setup>
<!-- specify database connection for this resource -->
                       <connection>
<!-- do not create new connection, use predefined core setup connection -->
                           <use>core_setup</use>
                       </connection>
                    </newmodule_setup>
                    <newmodule_write>
                         <connection>
                              <use>core_write</use>
                         </connection>
                    </newmodule_write>
                    <newmodule_read>
                         <connection>
                               <use>core_read</use>
                         </connection>
                    </newmodule_read>
                </resources>
           </global>
      </config>

Adapter Class:
To obtain module functionality you can write necessary method in various classes as magento convention.
1. Create necessary model class in app/code/local/M4U/NewModule/Model/
2. Create Block in app/code/local/M4U/NewModule/Block/
3. Create Helper in app/code/local/M4U/NewModule/Helper/
4. Place necessary updated database sql file in app/code/local/M4U/NewModule/sql/

Frontend Template Define:

1. Define page layout in app/design/frontend/M4U/default/layout/NewModule.xml

<?xml version="1.0"?>
   <layout version="0.1.0">
     <newmodule_index_usercredit>
        <reference name="root">
            <action method="setTemplate"><template>page/1column.phtml</template></action>
        </reference>
        <update handle="customer_account"/>
        <reference name="content">
            <block type="newmodule/blockClassName" name="usercredit" template="newmodule/usercredit.phtml"/>
        </reference>
     </newmodule_index_usercredit>
</layout>

2. Create template file app/design/frontend/M4U/default/template/newmodule/usercredit.phtml

Troubleshooting

• Dont put your module in /Mage. It belongs in app/code/community/ or app/code/local/
• Make sure your module’s first letter is capitlized. newmodule apparently will not work, it must start with a capital letter Newmodule.
• If your module is not showing in configuration>advanced then check your config.xml
• Make sure you clear the cache.

In this post i described general module customization theory of Magento. For more clarification you can see next post  “write HelloWord module” in this blog.

Magento Block override rules

Magento Block override rule is similar as helper and model override. Magento follows MVC pattern but Block is the extra layer in Magento. Block class render data for a particular template block. Magento introduces great blocking system in template design system.

Blocks are a way by which Magento distinguishes the array of functionalities in the system and creates a modular way to manage it from both visual and functional stand point. There are two types of blocks and they work together to create the visual output.

* Structural Blocks
These are blocks created for the sole purpose of assigning visual structure to a store page such as header, left column, main column and footer.
* Content Blocks
These are blocks that produce the actual content inside each structural block. They are representations of each feature functionality in a page and employs template files to generate (X)HTML to be inserted into its parent structural block. Category list, mini cart, product tags and product listing…etc are each its own content block.

Instead of including template after template as a typical eCommerce application would in order to gather the whole (X)HTML output, Magento gathers and arranges page content through blocks.

How to override a block ?:
Here i used Customer module as example. And here i describe various customer block class override system as example.
a) Customer register form block (Mage_Customer_Block_Form_Register)
b) Customer view form block (Mage_Customer_Block_Form_View)
c) Customer address edit block (Mage_Customer_Block_Address_Edit)
d) Customer account dashboard info block (Mage_Customer_Block_Account_Dashboard_Info)
e) Customer account dashboard address block (Mage_Customer_Block_Account_Dashboard_Address)
f) Customer widget name block (Mage_Customer_Block_Widget_Name)

Lets start step by step…………

1. At first create new module to process override work and write below code in app/etc/modules/M4U_Customer.xml

<?xml version="1.0"?>
       <config>
             <modules>
                  <M4U_Customer>
                       <active>true</active>
                       <codePool>local</codePool>
                  </M4U_Customer>
            </modules>
     </config>

2. Configure in app/code/local/M4U/Customer/etc/config.xml. Here, I mention 5/6 block override syntax as example. Keep only those classes whose classes you want to override.

<?xml version="1.0"?>
    <config>
        <modules>
            <M4U_Customer>
                <version>0.1.0</version>
            </M4U_Customer>
        </modules>

        <global>
           <blocks>
              <customer>
                  <rewrite>
                      <form_register>M4U_Customer_Block_Form_Register</form_register>
                      <form_view>M4U_Customer_Block_Form_View</form_view>
                      <address_edit>M4U_Customer_Block_Address_Edit</address_edit>
                      <account_dashboard_address>M4U_Customer_Block_Account_Dashboard_Address</account_dashboard_address>
                      <account_dashboard_info>M4U_Customer_Block_Account_Dashboard_Info</account_dashboard_info>
                      <widget_addressname>M4U_Customer_Block_Widget_Name</widget_addressname>
                 </rewrite>
              </customer>
           </blocks>
        </global>
  </config>

3. Now write your new block class and define all override methods

a) Customer register form block override

class M4U_Customer_Block_Form_Register extends Mage_Customer_Block_Form_Register
{
   // override existing method
  //write new function
    public function newmethod()
    {
        return true;
    }
}

b) Customer view form block (Mage_Customer_Block_Form_View)

class M4U_Customer_Block_Form_View extends Mage_Customer_Block_Account_Dashboard
{
   // override existing method
  //write new function
    public function newmethod()
    {
        return true;
    }
}

c) Customer address edit block (Mage_Customer_Block_Address_Edit)

class M4U_Customer_Block_Address_Edit extends Mage_Customer_Block_Address_Edit
{
   // override existing method
  public function getAddressStatus()
   {
      return $this->getRequest()->getParam('address');
   }

  //write new function
    public function newmethod()
    {
        return true;
    }
}

d) Customer account dashboard info block (Mage_Customer_Block_Account_Dashboard_Info)

class M4U_Customer_Block_Account_Dashboard_Info extends Mage_Customer_Block_Account_Dashboard_Info
{
   // override existing method
  //write new function
    public function newmethod()
    {
        return true;
    }
}

e) Customer account dashboard address block (Mage_Customer_Block_Account_Dashboard_Address)

class M4U_Customer_Block_Account_Dashboard_Address extends Mage_Customer_Block_Account_Dashboard_Address
{
   // override existing method
  //write new function
    public function newmethod()
    {
        return true;
    }
}

f) Customer widget name block (Mage_Customer_Block_Widget_Name)

class M4U_Customer_Block_Widget_Name extends Mage_Customer_Block_Widget_Abstract
{
   // override existing method
  public function showMiddlename()
    {
        return $this->_showConfig('middlename_show');
    }

  //write new function
    public function newmethod()
    {
        return true;
    }
}

What is class override in Magento ?

Magento e-commerce support class override theory. Override means “suspension of an automatic function”. That means you can overlap any magento function using your own modified function by following magento’s class override theory.
For example, suppose you want to extend magento registration system, so need to change registerPostAction() function in Mage_Customer class. Magento suggest you should not touch any magento core code to extend any feature. But you can extend or change any classes as you needed just creating a new class outside of Mage_Core. For this you should follow magento class override rules. By following rules you can create a new customer class like M4U_Customer outside of core. And write your extended function registerPostAction() in M4U_Customer class. Now, when you call registerPostAction() function then Magento automatically will render your own function and suspend calling of Mage_Customer function. Its called magento class overriding.

Magento is unique in opensource world for it’s class override facilities. If you customize magento by following override rules then you can easily upgrade magento version on your live site.

To know about specific class override rules you can see controller override, model override, block override, helper override, etc xml override posts in this blog.