## 4.2.15.16.3.3.7  Patching a Message Class
The following code sample illustrates how PATCH operations can be used to change parts of an existing messages class:
```
 Sample Code "! <p class="shorttext synchronized" lang="EN"> "!  XCO Documentation CP: Generation PATCH "! </p> "! "! Code sample for executing PATCH operations for messages classes (MSAGs). "! "! IMPORTANT: The values of the constants CO_PACKAGE and CO_TRANSPORT must be replaced "! with an existing package and a modifiable Workbench transport matching the transport "! target of the package. CLASS zcl_xco_doc_cp_cs_gen_patch DEFINITION PUBLIC FINAL INHERITING FROM cl_xco_cp_adt_simple_classrun CREATE PUBLIC. PUBLIC SECTION. METHODS: constructor. PROTECTED SECTION. METHODS: main REDEFINITION. PRIVATE SECTION. CONSTANTS: co_package            TYPE sxco_package VALUE 'ZXCO_CP_PACKAGE',
```
```
co_transport          TYPE sxco_transport VALUE 'X08K900164', co_message_class_name TYPE sxco_mc_object_name VALUE 'ZXCO_DEMO_MSG_CLS'. DATA: mo_environment TYPE REF TO if_xco_cp_gen_env_dev_system. METHODS: put_msag, patch_msag_1, patch_msag_2, read_msag IMPORTING out TYPE REF TO if_xco_adt_classrun_out. ENDCLASS. CLASS zcl_xco_doc_cp_cs_gen_patch IMPLEMENTATION. METHOD constructor. super->constructor( ). mo_environment = xco_cp_generation=>environment->dev_system( co_transport ). ENDMETHOD. METHOD main. put_msag( ). read_msag( out ). patch_msag_1( ). read_msag( out ). patch_msag_2( ). read_msag( out ). ENDMETHOD. METHOD put_msag. DATA(lo_put_operation) = mo_environment->for-msag->create_put_operation( ). DATA(lo_specification) = lo_put_operation->add_object( co_message_class_name )->set_package( co_package )->create_form_specification( ). lo_specification->set_short_description( 'Generated message class' ). lo_specification->add_message( '000' )->set_short_text( 'First message' ). lo_put_operation->execute( ). ENDMETHOD. METHOD patch_msag_1. DATA(lo_patch_operation) = mo_environment->for-msag->create_patch_operation( ). DATA(lo_object) = lo_patch_operation->add_object( co_message_class_name ). " Update existing message. lo_object->for-update->message( '000' )->set_short_text( 'First message (UPDATED)' ). " Insert new message. lo_object->for-insert->add_message( '001' )->set_short_text( 'Second message' ).
```
```
" Modify non-existing message (will insert the message). lo_object->for-modify->add_message( '002' )->set_short_text( 'Third message' ). lo_patch_operation->execute( ). ENDMETHOD. METHOD patch_msag_2. DATA(lo_patch_operation) = mo_environment->for-msag->create_patch_operation( ). DATA(lo_object) = lo_patch_operation->add_object( co_message_class_name ). " Modify non-existing message (will update the message). lo_object->for-modify->add_message( '002' )->set_short_text( 'Third message (UPDATED)' ). " Delete message lo_object->for-delete->add_message( '000' ). lo_patch_operation->execute( ). ENDMETHOD. METHOD read_msag. DATA(lo_message_class) = xco_cp_abap_repository=>object->msag>for( co_message_class_name ). out->write( |Messages of message class { lo_message_class->name }:| ). LOOP AT lo_message_class->messages->all->get( ) INTO DATA(lo_message). out->write( |Message { lo_message->number }:| ). DATA(ls_message) = lo_message->content( )->get( ). out->write( ls_message ). ENDLOOP. ENDMETHOD. ENDCLASS.
```