ABAP various ways to Exit processing Blocks

No matter which programming language you are working with, at the end of the day your job revolves around manipulating its processing block to achieve the desired results. One of them is exiting it.

In this post, I wanted to talk about various ways you could exit an ABAP processing block. 

But first,

What is a Processing Block?

    Modularization unit of an ABAP program that cannot be split or nested. Processing blocks are

    - Procedures like subroutines or methods,

    - Dialog modules declared for screens, and 

    - Event blocks like reporting events such as load-of-program, start-of-selection,  etc.

    To summarise, 

        Each non-declared statement in an ABAP program is part of a processing block.

Now, coming back to the point of the post.

Below are the different ABAP statements that you can use to exit the processing block.

-> Always Use RETURN
-> CHECK can be used as a guard clause at the start of the block
-> Use EXIT only inside LOOP blocks
-> Never use STOP.

RETURN:

  Syntax:  RETURN.

  Example:

	METHOD show_list.
	"IMPORTING it_data TYPE ANY TABLE.
	DATA:
	lo_alv_list TYPE REF TO cl_gui_alv_grid.
	" Leave if input has no data.
	IF it_data IS INITIAL.
	RETURN.
	ENDIF.
	cl_salv_table=>factory( IMPORTING r_salv_table = lo_salv " Basis Class Simple ALV Tables
	CHANGING t_table = it_data
	).
	lo_salv->display( ).
	ENDMETHOD.

view raw return_statement_simple.abap hosted with ❤ by GitHub

  Features:

  - This statement ends the current processing block immediately.

  - Can be used at any point in the processing block. 

  - The statement ends the block irrespective of the statement block or control structure it is used inside.

     In Other words, 

        Even if you use the statement RETURN inside loops, it will end the whole processing block 

        that contains the loop, not just the loop block. 

  Things to Note: 

   - You cannot exit the load-of-program event block using RETURN.

   - If you use RETURN to exit start-of-selection, No further reporting events are triggered. 

     Instead, the list processor is called directly.

  My Opinion:

   - This is by far the best way to exit procedures. 

EXIT: 

  Syntax:   EXIT.

  Example:

	METHOD get_Data.
	DATA:
	lt_mara TYPE STANDARD TABLE OF mara,
	lt_marc TYPE STANDARD TABLE OF marc.
	SELECT *
	FROM MARA
	INTO TABLE LT_MARA
	WHERE MATNR = iv_matnr.
	" EXIT on unsuccesful Query.
	IF SYST-SUBRC <> 0.
	EXIT.
	ENDIF.
	SELECT *
	from MARC
	INTO TABLE LT_MARC
	FOR ALL ENTRIES IN LT_MARA
	WHERE MATNR = LT_MARA-MATNR.
	" EXIT on unsuccesful Query.
	IF SYST-SUBRC <> 0.
	EXIT.
	ENDIF.
	ENDMETHOD.

view raw abap_exit_stmnt_simple.abap hosted with ❤ by GitHub

  Features: 

   - If used outside a loop block, the statement immediately terminates the current processing block.

   - If used inside a loop block, the statement terminates it. 

  Things to Note:

   - You cannot exit the load-of-program event block using EXIT. 

   - If you use the EXIT to exit the start-of-selection event, no further reporting events

     are triggered. Instead, the list processor is called directly.       

  My Opinion: 

  - The EXIT statement should only be used to terminate loop blocks prematurely.

CHECK: 

  Syntax:   CHECK log_exp.

 Example:

	METHOD get_Data.
	DATA:
	lt_mara TYPE STANDARD TABLE OF mara,
	lt_marc TYPE STANDARD TABLE OF marc.
	CHECK iv_matnr is not intial." Check if input has value.
	SELECT *
	FROM MARA
	INTO TABLE lt_mara
	WHERE MATNR = iv_matnr.
	" Leave on unsuccesful Query.
	CHECK syst-subrc = 0.
	SELECT *
	from MARC
	INTO TABLE lt_marc
	FOR ALL ENTRIES IN lt_mara
	WHERE MATNR = lt_mara-MATNR.
	" Leave on unsuccesful Query.
	CHECK syst-subrc = 0.
	ENDMETHOD.

view raw abap_check_stmnt_ex_simple.abap hosted with ❤ by GitHub

  Features:

  - If used outside a loop and the log_exp is false, the statement immediately terminates the

    current processing block.

  - If used inside a loop and the log_exp is false, the statement skips the current loop pass and

    moves on to the next loop pass.

  Things to Note: 

   - You cannot exit the load-of-program using CHECK.

  My Opinion:

  - The CHECK statement should be used either at the start of the processing block as a 

    guard clause or inside loop block to skip loop passes based on a certain condition.

STOP:

  Syntax:   STOP.

  Example:

	REPORT sy-repid.
	PARAMETERS:
	p_matnr TYPE matnr.
	DATA:
	lt_mara TYPE STANDARD TABLE OF mara.
	START-OF-SELECTION.
	SELECT *
	FROM mara
	INTO TABLE lt_mara
	WHERE matnr = p_matnr.
	IF syst-subrc <> 0.
	STOP. " Stop processing
	ENDIF.
	cl_demo_output=>display( lt_mara ) .

view raw stop_stmtnt_example.abap hosted with ❤ by GitHub

  Features: 

  - The STOP statement is only to be used in executable programs and in the following event blocks:

       at selection-screen (without additions),

       start-of-selection. 

       These event blocks are exited using STOP and the runtime environment triggers the event

        end-of-selection.

  - Using STOP at other places will lead to non-catchable exceptions and runtime errors:

       stop_no_report - Executed outside the process for an executable program.

       stop_within_called_dynpro - Executed during the process for a screen and 

       therefore outside the permitted events.

  My Opinion:

    Do not use the STOP statement unless absolutely necessary and there are no other options to 

    achieve the desired results.

In Conclusion,

    In ABAP, There are different options available for program-driven exiting of a processing block 

    with each having its own features.

    However from a robustness point of view RETURN statement is the best option, the second 

    choice being CHECK as a guard clause at the start of the block.

    I hope you liked the post and use this information while in your day-to-day work.