## 4.2.15.16.3.3.8  Patching Methods of Interfaces and Classes
The XCO Generation APIs allow to incrementally modify existing interfaces and classes through PATCH operations.
The following two code samples illustrate how methods of interfaces and classes can be patched. In each code sample, the MAIN method will execute one of four phases depending on the current state of the interface or class. To see each phase in action simply execute each class several times in a row.
Here is how it looks for interfaces:
```
 Sample Code "! Code sample for patching methods of an interface. "! "! IMPORTANT: The value of the constant CO_PACKAGE  must be replaced with an existing "! development package. CLASS zcl_xco_doc_cp_cs_patch_in_me 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 'ZMY_PACKAGE', co_interface_name TYPE sxco_ao_object_name VALUE 'ZIF_XCO_DMO_GEN_INTF_PATCH_MTD', co_first_method  TYPE sxco_ao_component_name VALUE 'FIRST_METHOD', co_second_method TYPE sxco_ao_component_name VALUE 'SECOND_METHOD', co_third_method  TYPE sxco_ao_component_name VALUE 'THIRD_METHOD'. DATA: mo_interface TYPE REF TO if_xco_ao_interface. METHODS: phase_1 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_2 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_3 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_4 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, get_environment IMPORTING out                  TYPE REF TO if_xco_adt_classrun_out RETURNING VALUE(ro_environment) TYPE REF TO if_xco_cp_gen_env_dev_system, get_transport_request IMPORTING out                        TYPE REF TO if_xco_adt_classrun_out RETURNING VALUE(ro_transport_request) TYPE REF TO if_xco_cp_tr_request. ENDCLASS. CLASS zcl_xco_doc_cp_cs_patch_in_me IMPLEMENTATION. METHOD constructor. super->constructor( ). mo_interface = xco_cp_abap=>interface( co_interface_name ). ENDMETHOD. METHOD main. IF mo_interface->exists( ) EQ abap_false. " In the first phase the interface is created via a PUT operation. phase_1( out ). out->write( |Executed phase 1| ). ELSEIF mo_interface->component->method( 'FIRST_METHOD' )->exists( ) EQ abap_false. " In the second phase two new methods are inserted into the interface " via a single PATCH operation.
```
```
phase_2( out ). out->write( |Executed phase 2| ). ELSEIF mo_interface->component->method( 'SECOND_METHOD' )->exists( ) EQ abap_true. " In the third phase one method is deleted, a new method is inserted and " an existing method is updated via a single PATCH operation. phase_3( out ). out->write( |Executed phase 3| ). ELSE. " In the fourth phase the interface is deleted via a DELETE operation. phase_4( out ). out->write( |Executed phase 4| ). ENDIF. ENDMETHOD. METHOD phase_1. DATA(lo_put_operation) = get_environment( out )->create_put_operation( ). DATA(lo_specification) = lo_put_operation->for-intf->add_object( mo_interface->name )->set_package( co_package )->create_form_specification( ). lo_specification->set_short_description( 'My interface' ). " Data lo_specification->add_data( 'ID' )->set_type( xco_cp_abap=>type-built_in->i )->set_read_only( ). lo_put_operation->execute( ). ENDMETHOD. METHOD phase_2. DATA(lo_patch_operation) = get_environment( out )->for-intf->create_patch_operation( ). DATA(lo_patch_operation_object) = lo_patch_operation->add_object( mo_interface->name ). " Insert first method DATA(lo_first_method) = lo_patch_operation_object->for-insert->add_method( co_first_method )->set_default_ignore( ). lo_first_method->add_importing_parameter( 'IMP_1' )->set_type( xco_cp_abap=>type-built_in->string ). lo_first_method->add_importing_parameter( 'IMP_2' )->set_type( xco_cp_abap=>type-built_in->string ). lo_first_method->add_changing_parameter( 'CHA_1' )->set_type( xco_cp_abap=>interface( 'IF_XCO_NEWS' ) ). lo_first_method->add_exception( 'CX_ABAP_INVALID_VALUE' ). " Insert second method DATA(lo_second_method) = lo_patch_operation_object->for-insert->add_method( co_second_method )->set_default_fail( ). lo_patch_operation->execute( ). ENDMETHOD. METHOD phase_3. DATA(lo_patch_operation) = get_environment( out )->for-intf->create_patch_operation( ).
```
```
DATA(lo_patch_operation_object) = lo_patch_operation->add_object( mo_interface->name ). " Update first method. DATA(lo_first_method) = lo_patch_operation_object->for-update->add_method( co_first_method )->set_default_fail( ). lo_first_method->for-update->add_importing_parameter( 'IMP_1' )->set_pass_by_value( )->set_optional( ). lo_first_method->for-delete->add_importing_parameter( 'IMP_2' ). lo_first_method->for-insert->add_importing_parameter( 'IMP_3' )->set_type( xco_cp_abap_dictionary=>data_element( 'SXCO_AO_OBJECT_NAME' ) ). lo_first_method->for-update->add_exception( 'CX_ABAP_INVALID_VALUE' )->set_resumable( ). " Delete second method. lo_patch_operation_object->for-delete->add_method( co_second_method ). " Insert third method. lo_patch_operation_object->for-insert->add_method( co_third_method )->set_default_fail( ). lo_patch_operation->execute( ). ENDMETHOD. METHOD phase_4. DATA(lo_delete_operation) = get_environment( out )->for-intf->create_delete_operation( ). lo_delete_operation->add_object( mo_interface->name ). lo_delete_operation->execute( ). ENDMETHOD. METHOD get_environment. DATA(lo_transport_request) = get_transport_request( out ). ro_environment = xco_cp_generation=>environment->dev_system( lo_transport_request->value ). ENDMETHOD. METHOD get_transport_request. DATA(lo_lock) = mo_interface->if_xco_cts_changeable~get_object( )->get_lock( ). IF lo_lock->exists( ) EQ abap_true. DATA(lv_transport) = lo_lock->get_transport( ). ro_transport_request = xco_cp_cts=>transport->for( lv_transport )->get_request( ). out->write( |Using transport request { ro_transport_request->value } (Interface is already locked).| ). ELSE. DATA(lo_transport_target) = xco_cp_abap_repository=>package>for( co_package )->read( )-property-transport_layer->get_transport_target( ). ro_transport_request = xco_cp_cts=>transports>workbench( lo_transport_target->value )->create_request( 'Generated transport request' ).
```
```
out->write( |Using newly generated transport request { ro_transport_request->value }.| ). ENDIF. ENDMETHOD. ENDCLASS.
```
and here is how it looks for classes:
```
 Sample Code "! Code sample for patching methods of a class. "! "! IMPORTANT: The value of the constant CO_PACKAGE  must be replaced with an existing "! development package. CLASS zcl_xco_doc_cp_cs_patch_cl_me 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 'ZMY_PACKAGE', co_class_name    TYPE sxco_ao_object_name VALUE 'ZCL_XCO_DMO_GEN_CLAS_PATCH_MTD', co_first_method  TYPE sxco_clas_method_name VALUE 'FIRST_METHOD', co_second_method TYPE sxco_clas_method_name VALUE 'SECOND_METHOD', co_third_method  TYPE sxco_clas_method_name VALUE 'THIRD_METHOD'. DATA: mo_class TYPE REF TO if_xco_ao_class. METHODS: phase_1 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_2 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_3 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, phase_4 IMPORTING out TYPE REF TO if_xco_adt_classrun_out, get_environment IMPORTING out                   TYPE REF TO if_xco_adt_classrun_out RETURNING VALUE(ro_environment) TYPE REF TO if_xco_cp_gen_env_dev_system, get_transport_request IMPORTING out                         TYPE REF TO if_xco_adt_classrun_out RETURNING VALUE(ro_transport_request) TYPE REF TO if_xco_cp_tr_request. ENDCLASS. CLASS zcl_xco_doc_cp_cs_patch_cl_me IMPLEMENTATION. METHOD constructor. super->constructor( ). mo_class = xco_cp_abap=>class( co_class_name ). ENDMETHOD. METHOD main. IF mo_class->exists( ) EQ abap_false. " In the first phase the class is created via a PUT operation. phase_1( out ).
```
```
out->write( |Executed phase 1| ). ELSEIF mo_class->definition->section-public->component>method( 'FIRST_METHOD' )->exists( ) EQ abap_false. " In the second phase two new methods are inserted into the class, one in the public section " and one in the private section, via a single PATCH operation. phase_2( out ). out->write( |Executed phase 2| ). ELSEIF mo_class->definition->section-private->component>method( 'SECOND_METHOD' )->exists( ) EQ abap_true. " In the third phase one method is deleted, a new method is inserted into the protected " section and an existing method is updated via a single PATCH operation. phase_3( out ). out->write( |Executed phase 3| ). ELSE. " In the fourth phase the class is deleted via a DELETE operation. phase_4( out ). out->write( |Executed phase 4| ). ENDIF. ENDMETHOD. METHOD phase_1. DATA(lo_put_operation) = get_environment( out )->create_put_operation( ). DATA(lo_specification) = lo_put_operation->for-clas->add_object( mo_class->name )->set_package( co_package )->create_form_specification( ). lo_specification->set_short_description( 'My class' ). " Data lo_specification->definition->section-public->add_data( 'ID' )->set_type( xco_cp_abap=>type-built_in->i )->set_read_only( ). lo_put_operation->execute( ). ENDMETHOD. METHOD phase_2. DATA(lo_patch_operation) = get_environment( out )->for-clas->create_patch_operation( ). DATA(lo_patch_operation_object) = lo_patch_operation->add_object( mo_class->name ). " First we specify the definition part of the class. " Insert the first method into the public section of the class. DATA(lo_first_method) = lo_patch_operation_object->for-insert->definition>section-public->add_method( co_first_method ). lo_first_method->add_importing_parameter( 'IMP_1' )->set_type( xco_cp_abap=>type-built_in->string ). lo_first_method->add_importing_parameter( 'IMP_2' )->set_type( xco_cp_abap=>type-built_in->string ). lo_first_method->add_changing_parameter( 'CHA_1' )->set_type( xco_cp_abap=>interface( 'IF_XCO_NEWS' ) ). lo_first_method->add_exception( 'CX_ABAP_INVALID_VALUE' ). " Insert the second method into the private section of the class. DATA(lo_second_method) = lo_patch_operation_object->for-insert>definition->section-private->add_method( co_second_method ). " After the definition has been specified we also specify the implementation part. If no implementation " is specified for an inserted method it will have an empty implementation (as is the case for " the second method). lo_patch_operation_object->for-insert->implementation->add_method( co_first_method )->set_source( VALUE #( ( `  " Source code goes here` ) ) ). lo_patch_operation->execute( ). ENDMETHOD. METHOD phase_3.
```
```
DATA(lo_patch_operation) = get_environment( out )->for-clas->create_patch_operation( ). DATA(lo_patch_operation_object) = lo_patch_operation->add_object( mo_class->name ). " As in phase 2, we first specify the definition part of the class. " Update first method. DATA(lo_first_method) = lo_patch_operation_object->for-update->definition>section-public->add_method( co_first_method ). lo_first_method->for-update->add_importing_parameter( 'IMP_1' )->set_pass_by_value( )->set_optional( ). lo_first_method->for-delete->add_importing_parameter( 'IMP_2' ). lo_first_method->for-insert->add_importing_parameter( 'IMP_3' )->set_type( xco_cp_abap_dictionary=>data_element( 'SXCO_AO_OBJECT_NAME' ) ). lo_first_method->for-update->add_exception( 'CX_ABAP_INVALID_VALUE' )->set_resumable( ). " Delete second method. lo_patch_operation_object->for-delete->definition->section-private->add_method( co_second_method ). " Insert the third method into the protected section of the class. lo_patch_operation_object->for-insert->definition->section-protected->add_method( co_third_method ). " Now the implementation part of the class is specified. lo_patch_operation_object->for-update->implementation->add_method( co_first_method )->set_source( VALUE #( ( `  RAISE EXCEPTION TYPE cx_abap_invalid_value.` ) ) ). lo_patch_operation_object->for-insert->implementation->add_method( co_third_method )->set_source( VALUE #( ( `  " Third method implementation` ) ) ). lo_patch_operation->execute( ). ENDMETHOD. METHOD phase_4. DATA(lo_delete_operation) = get_environment( out )->for-clas->create_delete_operation( ). lo_delete_operation->add_object( mo_class->name ). lo_delete_operation->execute( ). ENDMETHOD. METHOD get_environment. DATA(lo_transport_request) = get_transport_request( out ). ro_environment = xco_cp_generation=>environment->dev_system( lo_transport_request->value ). ENDMETHOD. METHOD get_transport_request. DATA(lo_lock) = mo_class->if_xco_cts_changeable~get_object( )->get_lock( ). IF lo_lock->exists( ) EQ abap_true. DATA(lv_transport) = lo_lock->get_transport( ). ro_transport_request = xco_cp_cts=>transport->for( lv_transport )->get_request( ). out->write( |Using transport request { ro_transport_request->value } (Class is already locked).| ). ELSE. DATA(lo_transport_target) = xco_cp_abap_repository=>package>for( co_package )->read( )-property-transport_layer->get_transport_target( ). ro_transport_request = xco_cp_cts=>transports>workbench( lo_transport_target->value )->create_request( 'Generated transport request' ). out->write( |Using newly generated transport request { ro_transport_request->value }.| ). ENDIF. ENDMETHOD.
```