I'm working on a module and I need a block file to be overridden in order to add new functionality. I know how to override blocks, model and controllers but I want to know that what will happen if the class I'd extended was being used by another module class?
The above scenario is as follows:
In my module config.xml I'd overridden a block file as:
<blocks>
<checkout>
<rewrite>
<cart_shipping>Company_Module_Block_Cart_Shipping</cart_shipping>
</rewrite>
</checkout>
</blocks>
and override a method getEstimateRates()
but there's another module whose block file extends Mage_Checkout_Block_Cart_Shipping. My question is -
"Will that class be able to see the changes made in the overridden class in my module?"
OR
"Do I have to override the other modules block file?"
One of yours or another extend block will not work. It can be fixed by extending yours or another block from one of them.
For example Company_Module_Block_Cart_Shipping is your block and Other_Module_Block_Cart_Shipping is other block.
If Other_Module_Block_Cart_Shipping is extended from core, you have to extend your Company_Module_Block_Cart_Shipping from Other_Module_Block_Cart_Shipping
Magento makes a config.xml tree of all the config.xml of enabled modules.
Mage_All.xml is loaded first, then all Mage.*.xml and preceding it your custom module .xml as per alphabetic sequence.
The sequence can be changed if you have given a depends tag in etc/modules/module definition xml.
Hope this clears your doubt.