Who can I overide function _loadNodes in flat.php

[GTibo]

I am new in overriding Magento code.  

I function _loadNodes i just want to change the sort order which works when changing the core file, but as this is not the correct approach i want to override the class/function.

I currently have as config.xml

<config>	
	<modules>
	  <MyModule_Catalog>
		  <version>0.1.0</version>
	  </MyModule_Catalog>
  </modules>
  <global>
    <models>
      <catalog>
        <rewrite>
          <resource_category_flat>MyModule_Catalog_Model_Resource_Category_Flat</resource_category_flat>
        </rewrite>
      </catalog>
    </models>
  </global>  
</config>

Flat.php 

class MyModule_Catalog_Model_Catalog_Resource_Category_Flat extends Mage_Index_Model_Resource_Abstract
{

Xml file in etc\modules

<config>
  <modules>
    <MyModule_Catalog>
      <active>true</active>
      <codePool>local</codePool>
      <depends>
        <Mage_Catalog />
      </depends>    
    </MyModule_Catalog>
  </modules>
</config>

it doesn't run the new code, it doesn't override 

[qaisar_satti]

Here are your two mistakes

First Class Name In config.xml  MyModule_Catalog_Model_Resource_Category_Flat

<resource_category_flat>MyModule_Catalog_Model_Resource_Category_Flat</resource_category_flat>

 And class name in your file  and

So here is you class look like

class MyModule_Catalog_Model_Catalog_Resource_Category_Flat extends Mage_Index_Model_Resource_Abstract
{

Change it and second it must be extends with rewrite class Mage_Catalog_Model_Resource_Category_Flat

class MyModule_Catalog_Model_Resource_Category_Flat extends Mage_Catalog_Model_Resource_Category_Flat
{