Webdynpro ABAP ALV tutorial - simple update or use changelog ?

Question

I was working through the alv tutorials for webdynpro abap, and while trying to complete the
"Editing ALV in Web Dynpro for ABAP", I got to page 8 of the pdf document where it explains how to do the ONDATACHECK event handler, and it comments out the portion for updating/saving the data (as noted below), and does not explain anything further about the save.
* save data to database
{* update... => only simlate, to not change the flight data model
* content!
Now, I am new to webdynpro abap, and don't know if I am supposed to utlize the changelog for this, or if a simple update will work.
Any Ideas ?

Answer 1

Thank you for your answer - I am guessing from your response that a method would need to be built - similar to one which I found in the SWDP_DEMO_TUTORIALS for a webdynpro called WDT_TABLE (see below) - where a check of the table changes would need to be made before an update to the table - rather than a simple one line update statement placed at that point in the code.
METHOD save_changes.
  DATA: table_node           TYPE REF TO if_wd_context_node,
        read_sbook           TYPE
if_componentcontroller=>elements_sbook_node,
        aux_read_sbook       TYPE
if_componentcontroller=>elements_sbook_node,
        wa_read_sbook        TYPE LINE OF
if_componentcontroller=>elements_sbook_node,
        context              TYPE REF TO if_wd_context,
        change_line          TYPE LINE OF wdr_context_change_list,
        changes              TYPE wdr_context_change_list,
        aux_changes          TYPE wdr_context_change,
        lv_change_tab_size   TYPE sy-tfill,
        aux_string           TYPE string,
        lv_node_size         TYPE sy-tfill,
        aux_div              TYPE int4,
        aux_index            TYPE i,
        l_current_controller TYPE REF TO if_wd_controller,
        l_message_manager    TYPE REF TO if_wd_message_manager,
        text                 TYPE string,
        it_int TYPE STANDARD TABLE OF i WITH KEY table_line.
* check whether context has changed
  context = wd_context->get_context( ).
  changes = context->get_context_change_log( ).
  LOOP AT changes INTO aux_changes.
    IF aux_changes-change_kind = 'A' AND aux_changes-node_name = 'SBOOK_NODE'.
      INSERT aux_changes INTO TABLE wd_this->sbook_delta.
    ENDIF.
  ENDLOOP.
* get the complete context in 'read_sbook' table
  table_node = wd_context->get_child_node( name = 'MY_BOOKING_NODE' ).
  table_node = table_node->get_child_node( name = 'SBOOK_NODE' ).
  table_node->get_static_attributes_table( IMPORTING table = read_sbook
* get the size of table and changes
  DESCRIBE TABLE read_sbook LINES lv_node_size.
  LOOP AT wd_this->sbook_delta INTO change_line.
    APPEND change_line-element_index TO it_int.
  ENDLOOP.
  SORT it_int.
  DELETE ADJACENT DUPLICATES FROM it_int.
  DESCRIBE TABLE it_int LINES lv_change_tab_size.
* get message manager
  l_current_controller ?= wd_this->wd_get_api( ).
  CALL METHOD l_current_controller->get_message_manager
    RECEIVING
      message_manager = l_message_manager.
* decide which way to update databse
  IF lv_change_tab_size <> 0.
    aux_div = lv_node_size / lv_change_tab_size.
    IF aux_div <= 3.
* write complete table to database
      lv_change_tab_size = lv_node_size.
      CL_WDT_FLIGHT_MODEL=>write_sbook_complete( read_sbook ).
    ELSE.
* write only the changed records to database
      LOOP AT it_int INTO aux_index.
        READ TABLE read_sbook INDEX aux_index INTO wa_read_sbook.
        APPEND wa_read_sbook TO aux_read_sbook.
      ENDLOOP.
      CL_WDT_FLIGHT_MODEL=>write_sbook_records_changed( aux_read_sbook )
    ENDIF.
    REFRESH wd_this->sbook_delta.
    REFRESH it_int.
    wd_this->sbook_changed = abap_false.
* report message
    aux_string = lv_change_tab_size .
    IF lv_change_tab_size = 1.
      CONCATENATE aux_string 'record written to database' INTO text.
    ELSE.
      CONCATENATE aux_string 'records written to database' INTO text.
    ENDIF.
    CALL METHOD l_message_manager->report_success
      EXPORTING
        message_text = text.
  ELSE.
*  report message
    CALL METHOD l_message_manager->report_success
      EXPORTING
        message_text = 'there are no changes to be written to database'.
  ENDIF.
ENDMETHOD.