ON (ABAP Keyword)

ON is a keyword used in SAP ABAP programming.This tutorial covers its introduction & syntax details.

ON

Basic form
ON CHANGE OF f.

 

Addition

… OR f1

Effect
Executes
the processing block enclosed by the ” ON CHANGE OF f ” and ” ENDON ”
statements whenever the contents of the field f change (control break
processing).

Normally, you use the statement to manipulate database fields during GET events or SELECT / ENDSELECT processing.

Note
There are special control structures for processing control breaks in LOOP s on internal tables or extract datasets AT ).

ON
CHANGE OF is unsuitable for recognizing control levels in loops of this
type because it always creates a global auxiliary field which is used
to check for changes. This global auxiliary field can only be changed
in the relevant ON CHANGE OF statement. It is not reset when the
processing goes into loops or subroutines, so unwanted effects can
occur if the loop or subroutine is executed again. Also, since it is
set to its initial value when created (like any other field), any ON
CHANGE OF processing will be executed after the first test, unless the
contents of the field concerned happen to be identical to the initial
value.

Example

TABLES T100.
SELECT * FROM T100 WHERE SPRSL = SY-LANGU AND
MSGNR < '010'
ORDER BY PRIMARY KEY.
ON CHANGE OF T100-ARBGB.
ULINE.
WRITE: / ‘***’, T100-ARBGB, ‘***’.
ENDON.
WRITE: / T100-MSGNR, T100-TEXT.
ENDSELECT.

Displays all messages with their numbers in the logon language, provided the number is less than ‘010’.
Each time the message class changes, it is output.

Addition
… OR f1

Effect
Also executes the code whenever the contents of the field f1 changes.
You can use this addition several times.

Example

* Logical database F1S
TABLES: SPFLI, SFLIGHT, SBOOK.
GET SBOOK.
ON CHANGE OF SPFLI-CARRID OR
SPFLI-CONNID OR
SFLIGHT-FLDATE.

ULINE.
WRITE: /5 SPFLI-CARRID, SPFLI-CONNID,
5 SFLIGHT-FLDATE, SPFLI-FLTIME,
5 SFLIGHT-SEATSMAX, SFLIGHT-SEATSOCC.
ENDON.
WRITE: / SBOOK-CUSTOMID.

The
code between ON CHANGE OF and ENDON is executed only if at least one of
the fields SPFLI-CARRID , SPFLI-CONNID or SFLIGHT-FLDATE has changed,
i.e. there is a different flight connection (which also has bookings).

Notes
Between
ON CHANGE OF and ENDON , you can use ELSE for case distinction. You can
also use ELSEIF statements in conjunction with special implementation
of ON , but should always try to avoid this because they may not be
supported in future.
Related AT – control breaks with internal tables
AT – control breaks with extracts