Use dynamic structure field in ABAP - structure

Question

I have a variable which should determine which field of a structure I use in further compilations.
So assume my variable is named currency and can have the values 'K', 'T' and 'H'. After checking which value it is, I want to use corresponding structure fields, e.g. mystructure-fieldk, mystructure-fieldt, mystructure-fieldi.
As for now, I just use IF..THEN to check the value of my variable currency and then just use the corresponding field of the structure, but therefore I have to repeat the coding of my loop 3 times which is just ugly.
LOOP AT itab ASSIGNING <fs>.
mystructure-fieldk = mystructure-fieldk + <fs>-otherfieldk.
ENDLOOP.
Is there a way that i can use the loop with a dynamic field? As in:
IF currency = 'K'.
DATA(mydynamicfield) = fieldk.
ENDIF.
and then use mydynamicfield in the loop:
LOOP AT itab ASSIGNING <fs>.
mystructure-mydynamicfield = mystructure-mydynamicfield + <fs>-otherfieldk.
ENDLOOP.
Or anything else? Thanks a lot!

Answer 1

Use the below piece of code
LOOP AT ITAB ASSIGNING <fs-structure>.
*-- determination of field name logic goes here let's say you have
*-- field name is in variable lv_field
ASSIGN COMPONENT (lv_field) of STRUCTURE <fs-structure> to <fs-field>.
IF <fs-field> IS ASSIGNED.
<fs-field> = 'the value you want to assign'.
ENDIF.
ENDLOOP.
Hope this clarifies.
Let's say you want to compute based on other field in the same structure
LOOP AT ITAB ASSIGNING <fs-structure>.
*-- determination of field name logic goes here let's say you have
*-- field name is in variable lv_field1 and other is lv_field2
ASSIGN COMPONENT (lv_field1) of STRUCTURE <fs-structure> to <fs-field1>.
ASSIGN COMPONENT (lv_field2) of STRUCTURE <fs-structure> to <fs-field2>.
IF <fs-field1> IS ASSIGNED ANDV<fs-field2> IS ASSIGNED .
<fs-field1> = <fs-field1> + <fs-field1>.
ENDIF.
ENDLOOP.
Note: the code is written to give an idea on how to proceed further in this issue. As Sandra pointed out this may result in compile issues please correct as necessary. I tried answering the question issuing a mobile device only. I don't have access to a compiler/system currently.

Answer 2

There's a better performance with a static reference to the components:
TYPES: BEGIN OF ty_structure,
fieldk TYPE i,
fieldt TYPE i,
fieldh TYPE i,
END OF ty_structure.
DATA: itab TYPE TABLE OF ty_structure,
mystructure TYPE ty_structure,
currency TYPE c LENGTH 1.
LOOP AT itab ASSIGNING FIELD-SYMBOL(<fs>).
CASE currency.
WHEN 'K'. ADD <fs>-fieldk TO mystructure-fieldk.
WHEN 'T'. ADD <fs>-fieldt TO mystructure-fieldt.
WHEN 'H'. ADD <fs>-fieldh TO mystructure-fieldh.
ENDCASE.
ENDLOOP.
If you want to simplify the code, you may use a macro (inline code):
LOOP AT itab ASSIGNING FIELD-SYMBOL(<fs>).
DEFINE m_add.
IF currency = 'K'.
ADD <fs>-field&1 TO mystructure-field&1.
ENDIF.
END-OF-DEFINITION.
m_add : K, T, H.
ENDLOOP.

Answer 3

I created working example with data. I believe, this will definitely help you.
dynamic field values are calculated and result is displayed at the end.
TYPES: BEGIN OF ty_itab,
currency TYPE c,
fieldk TYPE i,
fieldt TYPE i,
fieldh TYPE i,
END OF ty_itab.
TYPES: BEGIN OF ty_structure,
fieldk TYPE i,
fieldt TYPE i,
fieldh TYPE i,
END OF ty_structure.
DATA: itab TYPE TABLE OF ty_itab,
ls_structure TYPE ty_structure.
itab = VALUE #( ( currency = 'H' fieldk = 10 fieldt = 20 fieldh = 30 )
( currency = 'H' fieldk = 50 fieldt = 60 fieldh = 70 )
( currency = 'T' fieldk = 100 fieldt = 120 fieldh = 150 )
( currency = 'K' fieldk = 300 fieldt = 400 fieldh = 500 ) ).
LOOP AT itab ASSIGNING FIELD-SYMBOL(<fs>).
CASE <fs>-currency.
WHEN 'K'. ADD <fs>-fieldk TO ls_structure-fieldk.
WHEN 'T'. ADD <fs>-fieldt TO ls_structure-fieldt.
WHEN 'H'. ADD <fs>-fieldh TO ls_structure-fieldh.
ENDCASE.
ENDLOOP.
cl_demo_output=>display( ls_structure ).

Answer 4

You can try with below code:
TYPES: BEGIN OF ts_basic_line,
matnr TYPE mara-matnr,
lifnr TYPE lfa1-lifnr,
END OF ts_basic_line,
ty_basic_line TYPE TABLE OF ts_basic_line.
DATA: lt_basic_data TYPE ty_basic_line,
lo_structure TYPE REF TO cl_abap_structdescr,
lt_components TYPE abap_component_tab.
lt_basic_data = VALUE #( ( matnr = '111' lifnr = '333' ) ). " data for test
READ TABLE lt_basic_data ASSIGNING FIELD-SYMBOL(<fs_line>) INDEX 1.
IF sy-subrc EQ 0.
lo_structure ?= cl_abap_typedescr=>describe_by_data( <fs_line> ).
lt_components = lo_structure->get_components( ).
LOOP AT lt_components ASSIGNING FIELD-SYMBOL(<fs_strucutre_fields>).
LOOP AT lt_basic_data ASSIGNING FIELD-SYMBOL(<fs_data>).
ASSIGN COMPONENT <fs_strucutre_fields>-name OF STRUCTURE <fs_data> TO FIELD-SYMBOL(<fs_value>).
IF sy-subrc EQ 0.
" here your code, e.x. data conversion
<fs_value> = |{ <fs_value> ALPHA = IN }|.
ENDIF.
ENDLOOP.
ENDLOOP.
ENDIF.