Dynamic context binding in web dynpro alv

Question

I use dynamic context binding (see code below to show and edit the ALV table.
'DB_TABLE' is a tranparent table. It works fine.
But now this table should be expanded with additional fields which are only known at runtime and could be different from case to case.
How can I get these fields in the context dynamically?
  DATA:
        rootnode_info TYPE REF TO if_wd_context_node_info,
        dyn_node      TYPE REF TO if_wd_context_node,
        tablename   TYPE string.
  rootnode_info = wd_context->get_node_info( ).
  tablename = 'DB_TABLE'.
  cl_wd_dynamic_tool=>create_nodeinfo_from_struct(
    parent_info = rootnode_info
    node_name = tablename
    structure_name = tablename
    is_multiple = abap_true ).
  DATA:
        stru_tab TYPE REF TO data.
  FIELD-SYMBOLS: <tab> TYPE table.
  CREATE DATA stru_tab TYPE TABLE OF (tablename).
  ASSIGN stru_tab->* TO <tab>.
  SELECT * FROM (tablename) INTO CORRESPONDING FIELDS OF TABLE <tab>.
  dyn_node = wd_context->get_child_node( name = tablename ).
  dyn_node->bind_table( <tab> ).

Answer 1

You should create a structure dynamically and use this as the context structure. See the coding below, where a structure is created, which contains CARRID and CONNID.
DATA: node_info type ref to if_wd_context_node_info,
      struct_type TYPE REF TO cl_abap_structdescr,
      table_type  type ref to cl_abap_tabledescr,
      comp_tab    TYPE cl_abap_structdescr=>component_table,
      comp        LIKE LINE OF comp_tab,
      my_table    type ref to data,
      my_row      type ref to data.
  field-symbols: <table> type table,
                 <row> type data,
                 <flight> type sflight.
* build a structure description from the list of single fields
  comp-name = 'CARRID'.
  comp-type ?= cl_abap_datadescr=>describe_by_name( 'S_CARR_ID' ).
  APPEND comp TO comp_tab.
  comp-name = 'CONNID'.
  comp-type ?= cl_abap_datadescr=>describe_by_name( 'S_CONN_ID' ).
  APPEND comp TO comp_tab.
* note this structure contains the fields "CONNID" and "CARRID"
  struct_type = cl_abap_structdescr=>create( comp_tab ).
* now the nodeinfo is created
  node_info = wd_context->get_node_info( ).
  node_info = node_info->add_new_child_node(
    name                         = 'MY_NODE'
    IS_MANDATORY                 = ABAP_true
    IS_MULTIPLE                  = ABAP_true
    STATIC_ELEMENT_RTTI          = struct_type
    IS_STATIC                    = ABAP_false
* fill new node;
  data: l_node type ref to if_wd_context_node,
        l_flight type STANDARD TABLE OF sflight.
  l_node = wd_context->get_child_node( 'MY_NODE' ).
  l_flight = wd_assist->get_flights( ).
*  if you could create a local data type, would be fine, but if you have to do it dynamically ...
  struct_type = node_info->GET_STATIC_ATTRIBUTES_TYPE( ).
* create tabledescriptor from structdescription (standard table, no keys)
  table_type = cl_abap_tabledescr=>create( p_line_type = struct_type ).
  create data my_table type handle table_type.
  assign my_table->* to <table>.
  loop at l_flight assigning <flight>.
    create data my_row type handle struct_type.
    assign my_row->* to <row>.
    move-corresponding <flight> to <row>.
    append <row> to <table>.
  endloop.
  l_node->bind_table( <table> ).