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02_Structures.md
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- [Structures in Statements for Processing Internal Tables](#structures-in-statements-for-processing-internal-tables)
- [Including Structures](#including-structures)
- [Getting Structured Type Information and Creating Structures at Runtime](#getting-structured-type-information-and-creating-structures-at-runtime)
- [sy Structure](#sy-structure)
- [Executable Example](#executable-example)
## Introduction
@@ -1005,6 +1006,282 @@ ENDLOOP.
<p align="right"><a href="#top">⬆️ back to top</a></p>
## sy Structure
- The `sy` (or `syst`) structure is a built-in data object.
- The components of the structure represent ABAP system fields.
- These fields, filled by the [ABAP runtime framework](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_runtime_frmwk_glosry.htm), can be used to query system information and more.
- Typically, they should only be read, and not overwritten.
- Prominent system fields are the following
- `sy-subrc`: Return code of many ABAP statements; typically, the value 0 indicates success
- `sy-tabix`: Row index of internal tables
- `sy-index`: Loop pass index
- These ones and others can be used in [ABAP for Cloud Development](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabap_for_cloud_dev_glosry.htm). However, most of the fields should not be used in ABAP for Cloud Development (indicated by a syntax warning) because they refer to [Standard ABAP](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenstandard_abap_glosry.htm) contexts (e.g. classic dynpros and lists), or their values are not relevant in a cloud context.
- More information about the purpose of the individual components is available at [ABAP System Fields (F1 documentation for Standard ABAP)](https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abensystem_fields.htm).
The following example demonstrates a selection of ABAP system fields. It uses artifacts from the ABAP cheat sheet repository. Note the comments in the code because a syntax warning will be displayed when inserting the code in a demo class. It is meant to emphasize that multiple system fields should not to be used in ABAP for Cloud Development.
To try the example out, create a demo class named `zcl_some_class` and paste the code into it. After activation, choose *F9* in ADT to execute the class. The example is set up to display output in the console.
```abap
CLASS zcl_some_class DEFINITION
PUBLIC
FINAL
CREATE PUBLIC .
PUBLIC SECTION.
INTERFACES if_oo_adt_classrun.
PROTECTED SECTION.
PRIVATE SECTION.
ENDCLASS.
CLASS zcl_some_class IMPLEMENTATION.
METHOD if_oo_adt_classrun~main.
"In ABAP for Cloud Development, the following statement will show a syntax warning saying that
"sy should not be used. Here, it is used for demonstration purposes.
"In the example, RTTI is used to get all component names of the built-in data object sy. In the loop,
"ABAP statements are created (they represent simple assignments using the various sy components) and
"output to the console. You can insert all the output DATA(...) = ... statements in the demo class's
"main method implementation. The purpose is to demonstrate that most of the sy components should not be
"used in ABAP for Cloud Development. Most of the statements will show a syntax warning in ABAP for Cloud
"Development. Check the ABAP Keyword Documentation (for Standard ABAP) and the F2 information for the
"purpose of the individual sy components.
LOOP AT CAST cl_abap_structdescr( cl_abap_typedescr=>describe_by_data( sy ) )->components INTO DATA(co).
DATA(sycomp) = to_lower( co-name ).
DATA(code) = |DATA(sy{ sycomp }) = sy-{ sycomp }.|.
out->write( code ).
ENDLOOP.
out->write( |\n| ).
out->write( |\n| ).
"Demonstrating prominent sy components that can be used in ABAP for Cloud Development
"------------------------------------------------------------------------------
"------------------ sy-subrc: Return code of ABAP statements ------------------
"------------------------------------------------------------------------------
"Many ABAP statements set a sy-subrc value. Check the ABAP Keyword Documentation
"for individual statements. Usually, the value 0 indicates a successful execution.
DATA(some_string) = `ABAP`.
"FIND statements
"Found
FIND `P` IN some_string.
ASSERT sy-subrc = 0.
"Not found
FIND `p` IN some_string RESPECTING CASE.
ASSERT sy-subrc = 4.
DATA(some_itab) = VALUE string_table( ( `a` ) ( `b` ) ( `c` ) ( `d` ) ).
"READ TABLE statements
"Entry available
READ TABLE some_itab INTO DATA(wa1) INDEX 3.
ASSERT sy-subrc = 0.
"Entry not available
READ TABLE some_itab INTO DATA(wa2) INDEX 7.
ASSERT sy-subrc = 4.
"ABAP SQL statements
DELETE FROM zdemo_abap_tab1.
IF sy-subrc = 0.
out->write( `DELETE: All rows were deleted.` ).
ELSE.
out->write( `DELETE: No row was deleted because it was already empty.` ).
ENDIF.
INSERT zdemo_abap_tab1 FROM TABLE @( VALUE #( ( key_field = 1 ) ( key_field = 2 ) ) ).
IF sy-subrc = 0.
out->write( `INSERT: All rows of the internal table were inserted.` ).
ENDIF.
INSERT zdemo_abap_tab1 FROM TABLE @( VALUE #( ( key_field = 3 ) ( key_field = 3 ) ) ) ACCEPTING DUPLICATE KEYS.
IF sy-subrc = 4.
out->write( `INSERT ... ACCEPTING DUPLICATE KEYS: sy-subrc has the value 4 in this case. Not all rows of the ` &&
`internal table were inserted because a row with the key already exists.` ).
ENDIF.
DELETE FROM zdemo_abap_tab1 WHERE key_field = 3.
IF sy-subrc = 0.
out->write( `DELETE: The row matching the WHERE condition was deleted.` ).
ELSE.
out->write( `DELETE: No match according to the WHERE condition.` ).
ENDIF.
DELETE FROM zdemo_abap_tab1 WHERE key_field = 3.
IF sy-subrc = 0.
out->write( `DELETE: The row matching the WHERE condition was deleted.` ).
ELSE.
out->write( `DELETE: No match according to the WHERE condition.` ).
ENDIF.
"------------------------------------------------------------------------------
"--------------------------- sy-index: Loop indexes ---------------------------
"------------------------------------------------------------------------------
CLEAR some_string.
"DO loops
DO 5 TIMES.
some_string = some_string && sy-index.
ENDDO.
ASSERT some_string = `12345`.
CLEAR some_string.
DO 10 TIMES.
some_string = some_string && sy-index.
IF sy-index = 7.
EXIT.
ENDIF.
ENDDO.
ASSERT some_string = `1234567`.
CLEAR some_string.
DATA number TYPE i.
"WHILE loop
WHILE number < 9.
number = sy-index.
some_string = some_string && number.
ENDWHILE.
ASSERT some_string = `123456789`.
"------------------------------------------------------------------------------
"------------------- sy-tabix: Row index of internal tables -------------------
"------------------------------------------------------------------------------
"Demo standard internal table with 5 entries
DATA(std_itab) = VALUE string_table( ( `a` ) ( `b` ) ( `c` ) ( `d` ) ( `e` ) ).
"READ TABLE statement using a free key
READ TABLE std_itab INTO DATA(wa3) WITH KEY table_line = `b`.
ASSERT sy-tabix = 2.
"Demo hashed internal table with 5 entries
DATA(hashed_itab) = VALUE string_hashed_table( ( `a` ) ( `b` ) ( `c` ) ( `d` ) ( `e` ) ).
"READ TABLE statement using a free key
READ TABLE hashed_itab INTO DATA(wa4) WITH KEY table_line = `b`.
"Hashed tables do not have a primary table index.
ASSERT sy-tabix = 0.
CLEAR some_string.
"LOOP statements
LOOP AT std_itab INTO DATA(wa5).
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `12345`.
CLEAR some_string.
"Step addition
"In the example, the table is looped across backwards
"indicated by the negative value. The step size 1 indicates
"that each line is respected.
LOOP AT std_itab INTO DATA(wa6) STEP -1.
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `54321`.
CLEAR some_string.
"Forward loop, step size = 2
LOOP AT std_itab INTO DATA(wa7) STEP 2.
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `135`.
CLEAR some_string.
"FROM/TO additions
LOOP AT std_itab INTO DATA(wa8) FROM 2 TO 4.
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `234`.
CLEAR some_string.
"STEP/FROM additions
LOOP AT std_itab INTO DATA(wa9) STEP 2 FROM 2.
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `24`.
CLEAR some_string.
"Hashed table
LOOP AT hashed_itab INTO DATA(wa10).
some_string = some_string && sy-tabix.
ENDLOOP.
ASSERT some_string = `00000`.
"------------------------------------------------------------------------------
"------------------------ sy-dbcnt: Edited table rows -------------------------
"------------------------------------------------------------------------------
DELETE FROM zdemo_abap_tab1.
DATA(dbcnt) = sy-dbcnt.
out->write( |Dbtab rows deleted: { dbcnt }| ).
INSERT zdemo_abap_tab1 FROM TABLE @( VALUE #( ( key_field = 1 ) ( key_field = 2 ) ) ).
ASSERT sy-dbcnt = 2.
INSERT zdemo_abap_tab1 FROM TABLE @( VALUE #( ( key_field = 3 ) ( key_field = 3 ) ) ) ACCEPTING DUPLICATE KEYS.
ASSERT sy-dbcnt = 1.
MODIFY zdemo_abap_tab1 FROM @( VALUE #( key_field = 1 char1 = 'aaa' ) ).
ASSERT sy-dbcnt = 1.
UPDATE zdemo_abap_tab1 SET char2 = 'bbb'.
ASSERT sy-dbcnt = 3.
DELETE FROM zdemo_abap_tab1 WHERE num1 IS INITIAL.
ASSERT sy-dbcnt = 3.
"------------------------------------------------------------------------------
"------------- sy-fdpos: Occurrence in byte or character strings --------------
"------------------------------------------------------------------------------
"For example, relevant in comparison expressions such as CS (constains string).
"If the comparison is true, sy-fdpos contains the offset of the found value. If it
"is false, sy-fdpos contains the length of the searched string.
some_string = `###abap###`.
IF some_string CS `p`.
out->write( |The substring is found. Offset of first finding: { sy-fdpos }| ).
ELSE.
out->write( |The substring is not found. Length of searched string: { sy-fdpos }| ).
ASSERT sy-fdpos = strlen( some_string ).
ENDIF.
IF some_string CS `#`.
out->write( |The substring is found. Offset of first finding: { sy-fdpos }| ).
ELSE.
out->write( |The substring is not found. Length of searched string: { sy-fdpos }| ).
ASSERT sy-fdpos = strlen( some_string ).
ENDIF.
IF some_string CS `Y`.
out->write( |The substring is found. Offset of first finding: { sy-fdpos }| ).
ELSE.
out->write( |The substring is not found. Length of searched string: { sy-fdpos }| ).
ASSERT sy-fdpos = strlen( some_string ).
ENDIF.
ENDMETHOD.
ENDCLASS.
```
<p align="right"><a href="#top">⬆️ back to top</a></p>
## Executable Example
[zcl_demo_abap_structures](./src/zcl_demo_abap_structures.clas.abap)