If you want to modify data, sent between CRM and CMS you can use custom filters.
There are list of available filters:
* *RetailcrmFilterProcessOrder* - order array, which will be sent to CRM
* *RetailcrmFilterProcessCustomer* - customer array, which will be sent to CRM
* *RetailcrmFilterProcessCustomerCorporate* - corporate customer array, which will be sent to CRM
* *RetailcrmFilterProcessAddress* - address array, which will be sent to CRM
* *RetailcrmFilterProcessOffer* - offer array, which will be sent to CRM (saved into Icml file)
* *RetailcrmFilterCustomersHistory* - array with assembled history for customer, loaded from CRM
* *RetailcrmFilterOrdersHistory* - array with assembled history for order, loaded from CRM
* *RetailcrmFilterSaveCustomer* - built customer object, which will be saved to CMS
* *RetailcrmFilterSaveCustomerAddress* - built customer address object, which will be saved to CMS
* *RetailcrmFilterSaveCorporateCustomer* - built corporate customer object, which will be saved to CMS
* *RetailcrmFilterSaveCorporateCustomerAddress* - built corporate customer address object, which will be saved to CMS
To use filters you should define a new class in `<prestashop-root>/modules/retailcrm/custom/hooks`. Filename and classname must match the filter name.
Filter class should implement interface *RetailcrmFilterInterface*. In filter class you must define *filter()* function, which will take initial `$object` and return customized `$object`.
##### Classes
If you want to change the default behavior of a module classes and be sure that these changes won't be overwritten during the module upgrade process, you should **copy the original classes** that you are going to customize to the `<prestashop-root>/modules/retailcrm/custom/classes` directory.
From here you can modify the methods of the classes for your own purposes, and they will not be affected during the module upgrade process.
Keep in mind that:
* If the logic and classes of the module have changed a lot after an upgrade, your customized logic may cause the module to malfunction. **You should always check for changes after an upgrade and update your customized classes if needed.**
* This feature does not allow to customize the base class (file `retailcrm.php`). For this you can use the standard Prestashop override feature.
