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danrega
2024-01-02 16:44:13 +01:00
parent 8d1bc44331
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06_Dynamic_Programming.md
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@@ -153,18 +153,18 @@ ASSIGN num TO FIELD-SYMBOL(<fs_inl>).
TYPES c_len_3 TYPE c LENGTH 3.
DATA(chars) = 'abcdefg'.
FIELD-SYMBOLS <fs1> TYPE c_len_3.
FIELD-SYMBOLS <fs1> TYPE c_len_3.
"Implicit casting
ASSIGN chars TO <fs1> CASTING.
ASSIGN chars TO <fs1> CASTING. "abc
FIELD-SYMBOLS <fs2> TYPE data.
"Explicit casting
ASSIGN chars TO <fs2> CASTING TYPE c_len_3.
ASSIGN chars TO <fs2> CASTING TYPE c_len_3. "abc
DATA chars_l4 TYPE c LENGTH 4.
ASSIGN chars TO <fs2> CASTING LIKE chars_l4.
ASSIGN chars TO <fs2> CASTING LIKE chars_l4. "abcd
```
> **💡 Note**<br>
@@ -210,7 +210,8 @@ LOOP AT itab ASSIGNING <fs1>.
...
ENDLOOP.
"Inline declaration of a field symbol. It receives a suitable
"Inline declaration of a field symbol. The field symbol is implcitly typed
"with the generic type data.
"type automatically.
LOOP AT itab ASSIGNING FIELD-SYMBOL(<fs2>).
<fs2>-carrid = ...
@@ -686,7 +687,7 @@ ASSIGN ('DOBJ') TO FIELD-SYMBOL(<fs_inline>).
"The statements set the sy-subrc value. No exception occurs in
"case of an unsuccessful assignment.
ASSIGN ('DOESNOTEXIST') TO <fs>.
ASSIGN ('DOES_NOT_EXIST') TO <fs>.
IF sy-subrc <> 0.
...
ENDIF.
@@ -893,8 +894,8 @@ DATA(gen_comp) = CONV string( <gen>-('COL2') ).
"has a generic type. The components of the structure are accessed dynamically in
"a DO loop. The sy-index value is interpreted as the position of the component
"in the structure. Plus, using RTTI - as also shown further down - the component
"name is retrieved. Component names and the values are added to a string. As a
"prerequisite, all component values can be converted to type string.
"names are retrieved. Component names and the values are added to a string. As a
"prerequisite, all component values must be convertible to type string.
DATA struc2string TYPE string.
FIELD-SYMBOLS <strco> TYPE data.
ASSIGN st TO <strco>.
@@ -998,7 +999,7 @@ ENDIF.
"------- Table expressions ------
"Similar to READ TABLE statements, you can specify table lines with 3 alternatives:
"index read, read using free key, table key
"Also there, dynamic specification are possible regarding the key specifications.
"Also there, dynamic specifications are possible regarding the key specifications.
"Reading based on index with dynamic key specifications
"Specifying the secondary table index of a sorted secondary key
@@ -1137,7 +1138,7 @@ SELECT *
INTO TABLE @fli_tab.
"Excursion: Compatible target data objects
"In the examples above, the data object/type was created statically.
"In the examples above, the data object/type is created statically.
"Creating an anonymous data object with a CREATE DATA statement
"and specifiying the type dynamically.
@@ -1177,6 +1178,19 @@ SELECT *
WHERE (where_clause)
INTO TABLE NEW @DATA(tab_dyn_where).
"Dynamic ORDER BY clause
SELECT *
FROM zdemo_abap_fli
ORDER BY (`FLDATE`)
INTO TABLE NEW @DATA(tab_dyn_order).
"SELECT statement with miscellaneous dynamic specifications
SELECT (`CARRID, CONNID, FLDATE`)
FROM (`ZDEMO_ABAP_FLI`)
WHERE (`CARRID <> ``AA```)
ORDER BY (`FLDATE`)
INTO TABLE NEW @DATA(tab_dyn_misc).
"Further dynamic specifications in other ABAP SQL statements
"Creating a structure to be inserted into the database table
SELECT SINGLE *
@@ -1197,6 +1211,154 @@ DELETE FROM (table) WHERE (`CARRID = 'YZ'`).
<p align="right"><a href="#top">⬆️ back to top</a></p>
**Excursion**: To take up the use case mentioned in the introduction about retrieving the content of a database table, storing it in an internal table, and
displaying it when the database table name is specified dynamically at
runtime, see the following code snippet. Note the comments.
```abap
CLASS zcl_example_class DEFINITION
PUBLIC
FINAL
CREATE PUBLIC .
PUBLIC SECTION.
INTERFACES if_oo_adt_classrun.
PROTECTED SECTION.
PRIVATE SECTION.
ENDCLASS.
CLASS zcl_example_class IMPLEMENTATION.
METHOD if_oo_adt_classrun~main.
"The example retrieves the content of a database table, storing it in an
"internal table, and displaying it when the database table name is
"specified dynamically at runtime.
"Certainly, there are quite some ways to achieve it, and that work out
"of the box. For example, in ABAP for Cloud Development, you can implement
"the classrun if_oo_adt_classrun and output content using the out->write(...)
"method. You can also inherit from cl_demo_classrun in your class. In
"classic ABAP, you can, for example and additionally, use cl_demo_output or
"ALV.
"Notes:
"- The following example is just ABAP code tinkering with dynamic programming
" aspects. Note the disclaimer in the README of the cheat sheet repository.
" It is an example that sets its focus on a dynamic SELECT statement and
" processing internal tablecontent by dynamically accessing structure
" components.
"- The ways mentioned above are way more powerful (e.g. in most cases also
" nested and deep data objects can be displayed for demo purposes).
"- For simplicity, column contents are converted to string here if necessary,
" i.e. all column contents must be convertible to string.
"- For display purposes, the snippet uses the classrun methods to display
" results sequentially - instead of displaying the internal table
" content retrieved by the SELECT statement directly.
"- The example uses database tables from the cheat sheet repository. To fill
" them, you can use the method call zcl_demo_abap_aux=>fill_dbtabs( )..
zcl_demo_abap_aux=>fill_dbtabs( ).
"Data objects and types relevant for the example (length and offset for
"content display)
DATA str TYPE string.
TYPES: BEGIN OF comp_struc,
name TYPE string,
len TYPE i,
off TYPE i,
END OF comp_struc.
DATA it_comps TYPE TABLE OF comp_struc WITH EMPTY KEY.
"Database table of type string containing names of database tables;
"table is looped over to output content of all database tables
DATA(dbtabs) = VALUE string_table( ( `ZDEMO_ABAP_CARR` )
( `ZDEMO_ABAP_FLI` )
( `ZDEMO_ABAP_FLSCH` ) ).
LOOP AT dbtabs INTO DATA(dbtab).
"Retrieving database content of a dynamically specified database table
TRY.
SELECT *
FROM (dbtab)
INTO TABLE NEW @DATA(itab)
UP TO 5 ROWS.
CATCH cx_sy_dynamic_osql_semantics INTO DATA(sql_error).
CLEAR itab->*.
out->write( |Table { dbtab } does not exist.| ).
ENDTRY.
IF sql_error IS INITIAL.
"Getting table component names using RTTI methods
TRY.
DATA(type_descr_obj_tab) = CAST cl_abap_tabledescr(
cl_abap_typedescr=>describe_by_data( itab->* ) ).
DATA(tab_comps) = CAST cl_abap_structdescr(
type_descr_obj_tab->get_table_line_type( ) )->get_components( ).
LOOP AT tab_comps ASSIGNING FIELD-SYMBOL(<comp>).
APPEND VALUE #( name = <comp>-name len = strlen( <comp>-name ) ) TO it_comps.
ENDLOOP.
CATCH cx_sy_move_cast_error INTO DATA(error).
ENDTRY.
IF error IS INITIAL.
out->write( |\n| ).
out->write( |Retrieved content of database table { dbtab }:| ).
"Implementation for properly aligning the content
"The example is implemented to check the length of the column names as well as the
"length of the values in the columns. It determines the length of the longest string
"in each column. Depending on the length values, either the length of the column name
"or the length of the longest string in a column is stored in an internal table that
"contains information for calculating the offset.
LOOP AT tab_comps ASSIGNING FIELD-SYMBOL(<len>).
ASSIGN it_comps[ name = <len>-name ] TO FIELD-SYMBOL(<co>).
DATA(max_content) = REDUCE i( INIT len = <co>-len
FOR <line> IN itab->*
NEXT len = COND #( WHEN strlen( CONV string( <line>-(<co>-name) ) ) > len
THEN strlen( CONV string( <line>-(<co>-name) ) )
ELSE len ) ).
"Extend the length value to leave some more space
IF max_content > <co>-len.
<co>-len = max_content + 3.
ELSE.
<co>-len += 3.
ENDIF.
ENDLOOP.
"Calculating offset values
DATA max_str_len TYPE i.
LOOP AT it_comps ASSIGNING FIELD-SYMBOL(<off>).
DATA(tabix) = sy-tabix.
READ TABLE it_comps INDEX tabix - 1 ASSIGNING FIELD-SYMBOL(<prev>).
<off>-off = COND #( WHEN tabix = 1 THEN 0 ELSE <prev>-len + <prev>-off ).
max_str_len += <off>-len.
ENDLOOP.
"Providing enough space so that table row content can be inserted based on
"the offset specification
SHIFT str BY max_str_len PLACES RIGHT.
"Adding the column names first
LOOP AT it_comps ASSIGNING FIELD-SYMBOL(<header>).
str = insert( val = str sub = <header>-name off = <header>-off ).
ENDLOOP.
out->write( str ).
"Processing all lines in the internal table containing the retrieved table rows
LOOP AT itab->* ASSIGNING FIELD-SYMBOL(<wa>).
CLEAR str.
SHIFT str BY max_str_len PLACES RIGHT.
DO.
TRY.
str = insert( val = str sub = <wa>-(sy-index) off = it_comps[ sy-index ]-off ).
CATCH cx_sy_assign_illegal_component cx_sy_range_out_of_bounds cx_sy_itab_line_not_found.
EXIT.
ENDTRY.
ENDDO.
out->write( str ).
ENDLOOP.
ENDIF.
out->write( |\n| ).
CLEAR: str, it_comps.
ENDIF.
ENDLOOP.
ENDMETHOD.
ENDCLASS.
```
<p align="right"><a href="#top">⬆️ back to top</a></p>
### Dynamic Invoke
The following code snippet shows dynamically specifying [procedure](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenprocedure_glosry.htm "Glossary Entry") calls.