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Conversion Patterns

Lifecycle: CURRENT / RECOMMENDED. Older forms you will still meet are labelled where they appear. See 21-Classic-vs-Modern-ABAP.

📖 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

📝 Contextual snippet — zsm_e_document_id is a placeholder character-like data element.

DATA external_value TYPE string VALUE '12345'.
DATA internal_value TYPE string VALUE '000000000000012345'.
DATA document_id    TYPE c LENGTH 10 VALUE '12345'.

" ALPHA = IN  : external/display form -> internal form (pads leading zeros).
" A string has no fixed length, so give one with WIDTH
DATA(padded_value) = |{ external_value ALPHA = IN WIDTH = 18 }|.     " 000000000000012345

" A fixed-length field is padded to its own length
DATA(padded_id) = |{ document_id ALPHA = IN }|.                        " 0000012345

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

" NEW <type>( ) creates an anonymous DATA OBJECT and returns a reference to it
DATA(document_id_ref) = NEW zsm_e_document_id( padded_id ).

⚠️ ALPHA = IN on a string adds no zeros by itself. According to the ABAP Keyword Documentation, the result length is the WIDTH value, the length of a fixed-length target the template is assigned to, or otherwise the length of the operand. For the five-character string '12345' that is five characters, so nothing is padded.

🧩 CORRESPONDING with BASE

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

DATA notification_data TYPE notification.
DATA change_data       TYPE notification.

notification_data = VALUE notification( notif_no    = '0000001234'
                                        notif_type  = 'T1'
                                        description = 'Initial Notification' ).
change_data       = VALUE notification( notif_type  = 'T2'
                                        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 change_data, so it is CLEARED in the result.
notification_data = CORRESPONDING #( BASE ( notification_data ) change_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 change_data-notif_no IS NOT INITIAL.
  notification_data-notif_no = change_data-notif_no.
ENDIF.

⏱️ Timestamp ↔ Date/Time Conversion

DATA time_stamp TYPE timestampl.

" Date + time -> timestamp. A TIMESTAMPL target gets zero fractions of a second;
" an inline declaration here would be of type TIMESTAMP
CONVERT DATE sy-datum TIME sy-uzeit
        INTO TIME STAMP time_stamp TIME ZONE sy-zonlo.

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

📝 Contextual snippet — change_data with a component value, source, the placeholder data element zsm_e_posnr and the placeholder structure zsm_s_target are assumed.

DATA(quantity)    = CONV int4( change_data-value ).
DATA(item_number) = CONV zsm_e_posnr( '000010' ).
DATA(target)      = CORRESPONDING zsm_s_target( source ).

🧱 CONV in a Parameter Position

📝 Contextual snippet — validator and order are assumed; check_appointment has a completely typed parameter person_id.

" CONV # works here because the target type comes from the parameter's type
validator->check_appointment( person_id = CONV #( 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 — give the length with WIDTH or a fixed-length operand, since a string is not padded by itself.
  • 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 ALPHA = IN to pad a string without WIDTH.
  • 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