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Conversion Patterns

📖 Introduction

A grab-bag of frequently needed conversion patterns beyond the core ALPHA/CONV/CORRESPONDING basics already covered in 02-Data-Types.

🔢 ALPHA Conversion via a Data Element Constructor

DATA lv_external TYPE string VALUE '12345'.
DATA lv_internal TYPE string VALUE '000000000000012345'.

" ALPHA = IN  : external/display form -> internal form (pads leading zeros)
DATA(lv_padded)   = |{ lv_external ALPHA = IN }|.

" ALPHA = OUT : internal form -> external/display form (strips leading zeros)
DATA(lv_stripped) = |{ lv_internal ALPHA = OUT }|.

" NEW <type>( ) creates an anonymous DATA OBJECT and returns a reference to it
DATA(lr_docno) = NEW /scdl/dl_docno_int( CONV #( lv_padded ) ).

🧩 CORRESPONDING with BASE

TYPES: BEGIN OF ty_viqmel,
         notif_no    TYPE char10,
         notif_type  TYPE char2,
         description TYPE char40,
       END OF ty_viqmel.

DATA ls_viqmel TYPE ty_viqmel.
DATA ls_data   TYPE ty_viqmel.

ls_viqmel = VALUE ty_viqmel( notif_no    = '0000001234'
                             notif_type  = 'M1'
                             description = 'Initial Notification' ).
ls_data   = VALUE ty_viqmel( notif_type  = 'M2'
                             description = 'Updated Notification' ).

" BASE supplies the starting values; the source then overwrites EVERY
" identically-named component - including with initial values.
" Here notif_no is initial in ls_data, so it is CLEARED in the result.
ls_viqmel = CORRESPONDING #( BASE ( ls_viqmel ) ls_data ).

⚠️ CORRESPONDING #( BASE ( a ) b ) is not a "merge non-initial fields" operator. It starts from a and then assigns all matching components from b, initial ones included. BASE is useful when the source structure has fewer components than the target — the extra target components keep their values. If you genuinely want "only overwrite where the source has a value", write that condition explicitly:

IF ls_data-notif_no IS NOT INITIAL.
  ls_viqmel-notif_no = ls_data-notif_no.
ENDIF.

⏱️ Timestamp ↔ Date/Time Conversion

DATA lv_timestamp TYPE timestampl.

" Date + time -> timestamp
CONVERT DATE sy-datum TIME sy-uzeit
        INTO TIME STAMP lv_timestamp TIME ZONE sy-zonlo.

" Timestamp -> date + time, with inline declaration of the targets
CONVERT TIME STAMP lv_timestamp TIME ZONE sy-zonlo
        INTO DATE DATA(lv_datum) TIME DATA(lv_time).

💡 This is the standard conversion used when a UI/Gateway layer sends a timestampl value (for example 20240524131025.8750000) that has to become a plain date on the ABAP side.

🔄 Explicit Type Conversion (CONV)

DATA(lv_quantity) = CONV int4( ls_data-value ).
DATA(lv_posnr)    = CONV zsm_e_posnr( '000010' ).
DATA(ls_target)   = CORRESPONDING zsm_t_data( ls_source ).

🧱 CONV in a Parameter Position

" CONV # works here because the target type comes from the parameter's type
lo_validator->check_appointment( iv_person_id = CONV #( ls_order-person_id ) ).

✅ Best Practices

  • Prefer |{ value ALPHA = IN/OUT }| (string template) over the classical CONVERSION_EXIT_ALPHA_INPUT/OUTPUT function module call in new code — same result, less overhead.
  • Use CORRESPONDING to map structures instead of long field-by-field assignments — but read the BASE note above before assuming it merges.
  • Always specify TIME ZONE explicitly in CONVERT ... TIME STAMP — omitting it silently uses the wrong zone in multi-time-zone landscapes.
  • Use CONV #( ) where the target type is derivable from the context (a parameter, a typed assignment) and an explicit CONV <type>( ) where it is not.

⚠️ Common Mistakes

  • Applying ALPHA = IN twice (double padding), or mixing IN/OUT directions inconsistently across a codebase.
  • Expecting CORRESPONDING #( BASE ( a ) b ) to skip initial source components. It does not.
  • Forgetting TIME ZONE in timestamp conversions, causing off-by-hours bugs.
  • Using CONV #( '' ) on a data element without checking whether an initial value is valid for that domain.

🎤 Interview & Review Checkpoints

  • Explain what the ALPHA conversion exit does and why SAP key fields (material number, document number) use it.
  • Explain exactly what CORRESPONDING #( BASE ( ... ) ... ) does to components that are initial in the source.
  • Be ready to explain the difference between CONV, CORRESPONDING, and a conversion-exit function module — when is each the right tool?

🔗 Related Chapters