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Dropdown by key or Dropdown by index, that is the question of a WDA developer

Introduction 

During my experience as a Web Dynpro for ABAP developer, I often had the doubt if it was better to use the UI element DropDownByKey or its brother DropDownByIndex.    

In these last days, I realized that I always prefer and use the DropDownByKey, it doesn’t matter if the list is inside a table, an ALV table or a simple element in a view. Clearly the index approach is also working well but I feel it as a more complex task that requires spending more time, and I’m wondering to know about your experience.

As a reference, I’m sharing below the step-by-step guide to build a DDL even without necessarily entering the fixed values ​​associated to a domain of the field.

Implementation  

First of all, I created a WDA with its Assistance Class used to encapsulate the reading of a couple of well-known tables like MARA and T134T (Material Type Descriptions).  

The idea is to display all MARA records changing the field MTART in a DropDownByKey.         

DDL By Key picture1.png

I added the component usage SALV_WD_TABLE to create an ALV table and in assistance class I have implemented two methods:   

DDL By Key picture2.png

Method FILL_TABLE    

(output parameter –> ET_MARA  Type  MARA_TAB):

METHOD fill_table.
SELECT * FROM mara INTO TABLE et_mara.
ENDMETHOD.

Method GET_TYPE_MATERIAL

(output parameter –> LT_VALUE_SET  Type WDY_KEY_VALUE_TABLE):

METHOD get_type_material.
DATA: lt_t134t            TYPE TABLE OF t134t.
*  field-symbols: <fs_t134t> type t134.
FIELD-SYMBOLS: <fs_t134>  TYPE t134t.
DATA ls_value             TYPE wdy_key_value.
SELECT * FROM t134t INTO TABLE lt_t134t WHERE spras = 'E'.
SORT lt_t134t BY mtart.
LOOP AT lt_t134t ASSIGNING <fs_t134>.
MOVE <fs_t134>-mtart TO ls_value-key.
MOVE <fs_t134>-mtbez TO ls_value-value.
APPEND ls_value TO lt_value_set.
ENDLOOP.
ENDMETHOD.

I have created a context in Component controller called ALV_TABLE with structure of MARA table.

Now in the HANDLEDEFAULT method of my WINDOWS I’m calling a component controller method where we will call the two assistance class methods:

DATA lo_nd_alv_table TYPE REF TO if_wd_context_node.
DATA lt_alv_table TYPE wd_this->elements_alv_table.
*   navigate from <CONTEXT> to <ALV_TABLE> via lead selection
lo_nd_alv_table = wd_context->get_child_node( name = wd_this->wdctx_alv_table ).
lo_nd_alv_table->get_static_attributes_table( IMPORTING table = lt_alv_table ).
lt_alv_table = wd_assist->fill_table( ).
lo_nd_alv_table->bind_table( new_items = lt_alv_table set_initial_elements = abap_true ).
DATA lr_node_info TYPE REF TO if_wd_context_node_info.
DATA lt_value_set TYPE wdy_key_value_table.
lr_node_info = lo_nd_alv_table->get_node_info( ).
*------------------------------------------------------------------*
* set sales district ddl
*------------------------------------------------------------------*
lt_value_set = wd_assist->get_type_material( ).
*--- set attribute info
lr_node_info->set_attribute_value_set( name = `MTART` value_set = lt_value_set ).

How you can see, we are binding the context ALV_TABLE calling method wd_assist->fill_table( ).The last three rows are used to set values in my drop down by key.  

And this is the result:   

DDL By Key picture3.png

7 Comments
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  • I would also note that drop down by index does not allow you to highlight the field in any error that you encounter – as no possibility to flag the field in the raised message.

    Only use case I can see is where different drop-downs per line are required. (Can also be covered by cell variants and dropdown by keys if you have only a few variations – but usually better to use dropdown by index.)

      • Yes Chris, this works not only for the ALV table but also for all other tables. But I always prefer to use ALV tables because they are faster to develop. The only case, that I do not use it, is when I have to do the table popin because it is not supported in ALV tables 😉
  • A dropdown by key is to change the value of a single field in a specific record.

    A dropdown by index is to change the selected record in a table.

    however, you can “abuse” the DDI by adding a subnode containing the desired values and binding the DDI index to this subnode. as an added advantage, each record can now have a different valueset, whereas the DDK has the same valueset for each record in the node.