Table error - Context Path Cannot Be Resolved (Last Node Is Empty)

Question

Hi All,
I am dynamically building up a context node called PoList which is used to hold the contents of a table.
My BAPI is called and a routine transfers the contents of the BAPI context node across into the POList context node. This is rendered correctly on the screen. There is a routine which filters the results based on a vendor. The code works fine when some records are found but when no records are found, I get the error "Context Path POLIST.EBELN Cannot Be Resolved (Last Node Is Empty) ".
The cardinality of the PoList node is 0..N. This should mean that 0 records is valid.
The ABAP which fills the context is pasted below :
data:
    Node_Z_Bapi_Po_Combined             type ref to If_Wd_Context_Node,
    Node_Changing_Po                    type ref to If_Wd_Context_Node,
    Node_T_Header                       type ref to If_Wd_Context_Node,
    Elem_T_Header                       type ref to If_Wd_Context_Element,
    itab_C_T_Header    type If_Componentcontroller=>Elements_Polist,
   stru_C_T_Header    like line of itab_C_T_Header,
    Stru_T_Header                       type If_Componentcontroller=>Element_T_Header .
  data:
    Node_Polist                         type ref to If_Wd_Context_Node,
    Elem_Polist                         type ref to If_Wd_Context_Element,
    Stru_Polist                         type If_Componentcontroller=>Element_Polist.
  data:
lri_Element    type ref to if_Wd_Context_Element,
loa_Elements   type Wdr_Context_Element_Set.
navigate from <CONTEXT> to <Z_BAPI_PO_COMBINED> via lead selection
  Node_Z_Bapi_Po_Combined = wd_Context->get_Child_Node( Name = IF_COMPONENTCONTROLLER=>wdctx_Z_Bapi_Po_Combined ).
navigate from <Z_BAPI_PO_COMBINED> to <CHANGING_PO> via lead selection
  Node_Changing_Po = Node_Z_Bapi_Po_Combined->get_Child_Node( Name = IF_COMPONENTCONTROLLER=>wdctx_Changing_Po ).
navigate from <CHANGING_PO> to <T_HEADER> via lead selection
  Node_T_Header = Node_Changing_Po->get_Child_Node( Name = IF_COMPONENTCONTROLLER=>wdctx_T_Header ).
navigate from <CONTEXT> to <POLIST> via lead selection
  Node_Polist = wd_Context->get_Child_Node( Name = IF_COMPONENTCONTROLLER=>wdctx_Polist ).
  loa_Elements = node_T_Header->get_Elements( ).
  loop at loa_Elements[] into lri_Element.
    lri_Element->get_Static_Attributes(
      importing Static_Attributes = stru_C_T_Header ).
Get the vendor number
    if i_lifnr is initial.
      insert  stru_C_T_Header into table itab_C_T_Header[].
    elseif i_lifnr = stru_c_t_header-lifnr.
      insert stru_C_T_Header into table itab_C_T_Header[].
    endif.
  endloop.
  data : W_LINES TYPE I.
  describe table itab_c_t_header lines w_lines.
  if w_lines eq 0.
    node_Polist->set_lead_selection_index( 0 ).
    CALL METHOD NODE_POLIST->INVALIDATE.
  else.
    node_Polist->bind_Table( itab_C_T_Header ).
    clear itab_C_T_Header[].
  endif.
I would have though that invalidating the node would blank the context node and mean that the table is empty but instead I get an error.
Please help.
Richard

Answer 1

Hi Richard,
The problem here is that some UI element tries to bind against a node where the parent node is empty. You have to make sure that the last but one node has at least 1 element, otherwise you should hide the UI element (visibility = NONE).
If the lead selection were empty, the corresponding error message would tell you this, but it explicitely says: "Last Node is Empty", and you can trust it.
One possibility to have at least one element in the node is to change the cardinality to 1..n. If you have a supply function for this node, you have to make sure that there is at least 1 element (bind empty structure to the node), otherwise the framework creates the first element for you.
Ciao, Regina