✒️ABAP El control del flujo de datos

Data Flow Control

Conditionals

A condition in ABAP triggers the execution of specific statements or sets of statements based on the evaluation of a logical expression. These expressions result in either TRUE or FALSE.

When a logical expression is TRUE, a designated set of statements is executed; otherwise, an alternative set of statements is carried out. In ABAP, conditions can be represented using the IF-ENDIF statement. For instance:

DATA: v_grade(1) TYPE c VALUE 'B'.

START-OF-SELECTION.

IF v_grade = 'A'.
WRITE:/ 'Excellent!'.
ELSE.
WRITE:/ 'Keep Improving.'.
ENDIF.

To demonstrate nested conditions within IF-ENDIF using the ELSEIF statement:

DATA: v_grade(1) TYPE c VALUE 'B'.

START-OF-SELECTION.

IF v_grade = 'A'.
WRITE:/ 'Excellent!'.
ELSEIF v_grade = 'B' OR 'C'.
WRITE:/ 'Good Job!'.
ELSE.
WRITE:/ 'Work Harder.'.
ENDIF.

In this example, the system executes the statements below ELSE if none of the conditions is valid.

An alternative method is using the CASE-ENDCASE statement:

DATA: v_grade(1) TYPE c VALUE 'B'.

START-OF-SELECTION.

CASE v_grade.
WHEN 'A'.
WRITE:/ 'Excellent!'.
WHEN 'B' OR 'C'.
WRITE:/ 'Good Job!'.
WHEN OTHERS.
WRITE:/ 'Work Harder.'.
ENDCASE.

If none of the conditions is valid, the system executes the statements below WHEN OTHERS.

Regardless of the approach—IF-ENDIF or CASE-ENDCASE—logical operators are essential in ABAP:

• AND
• OR
• Equal = EQ
• Not equal <> NE
• Greater than > GT
• Lower than < LT
• Greater than or equal >= GE
• Lower than or equal <= or LE

* Si el sy-subrc es igual a cero
IF sy-subrc EQ 0 OR sy-subrc = 0. "Ambas expresiones lógicas son identicas
WRITE:/'='.
* Si el sy-subrc es distinto de cero
ELSEIF sy-subrc NE 0 OR sy-subrc <> 0. "Ambas expresiones lógicas son identicas
WRITE:/'<>'.
* Si el sy-subrc es mayor a cero
ELSEIF sy-subrc GT 0 OR sy-subrc > 0. "Ambas expresiones lógicas son identicas
WRITE:/'>'.
* Si el sy-subrc es menor a cero
ELSEIF sy-subrc LT 0 OR sy-subrc < 0. "Ambas expresiones lógicas son identicas
WRITE:/'<'.
* Si el sy-subrc es mayor o igual a cero
ELSEIF sy-subrc GE 0 OR sy-subrc >= 0. "Ambas expresiones lógicas son identicas
WRITE:/'>='.
* Si el sy-subrc es menor o igual a cero
ELSEIF sy-subrc LE 0 OR sy-subrc <= 0. "Ambas expresiones lógicas son identicas
WRITE:/'<='.
ENDIF.

Loops

A loop in programming signifies a sequence of code instructions that iteratively execute until the assigned condition becomes false. In ABAP, different loop structures are available.

• Using LOOP-ENDLOOP designed for working with internal tables:

LOOP AT it_students INTO wa_student WHERE grade >= 'C'.
WRITE:/ wa_student-id,
wa_student-name,
wa_student-grade.
ENDLOOP.

• Another loop structure in ABAP is DO-ENDDO, suitable for working with variables:

DO 10 TIMES.
v_counter = v_counter + 1.
WRITE:/ v_counter.
ENDDO.

• Controlling DO Exits:

DO.
ADD 1 TO gv_numero.

IF gv_numero = 4.
WRITE: / 'Es la vuelta 4'.
CONTINUE.
ENDIF.

IF gv_numero > 8.
EXIT.
ENDIF.

gv_resultado = 1 * gv_numero.
WRITE: / '1 x ', gv_numero, ': ', gv_resultado.
ENDDO.

• While there is an option to use WHILE-ENDWHILE in ABAP, it's rarely used in practice.

DATA: gv_numero TYPE n LENGTH 2,
gv_resultado TYPE n LENGTH 2.

WHILE gv_numero < 10.
ADD 1 TO gv_numero.
gv_resultado = 2 * gv_numero.
WRITE: / '2 x ', gv_numero, ': ', gv_resultado.
ENDWHILE.

Accessing INDEX iterator:

When you are in a loop for an internal table (LOOP AT), you should use SY-TABIX.

If you are in another loop (DO or WHILE), you should use SY-INDEX.

Control Statements

Control statements are employed to conclude the processing of a loop, subroutine, or an entire program. ABAP provides several control statements:

• CHECK: Verifies if a condition is true, skipping subsequent statements within a loop if false, and continuing with the next iteration.
• EXIT: Exits a loop when executed within it, exits a subroutine when executed within, and terminates the program outside of a loop or subroutine.
• CONTINUE: Exclusively used within a loop. After execution, the system proceeds with the next iteration of the loop.
• STOP: Concludes the running program, executing the END-OF-SELECTION event if present.
• LEAVE: Terminates the running program without executing the END-OF-SELECTION event.

Careful consideration is essential while utilizing CHECK, EXIT, CONTINUE, LEAVE, and STOP as they directly influence the control flow in an ABAP program.

E.g.

REPORT ztest_abap_jega_4.

DATA: v_nro_vuelta TYPE i.

START-OF-SELECTION.

CLEAR v_nro_vuelta.

DO 10 TIMES.
ADD 1 TO v_nro_vuelta.

IF v_nro_vuelta = 6.
EXIT.
ENDIF.
ENDDO.

WRITE:/'El numero de vuelta final del ciclo fue: ', v_nro_vuelta.
"El numero de vuelta final del ciclo fue: 6