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danrega
2024-06-27 16:31:47 +02:00
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06_Dynamic_Programming.md
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@@ -20,7 +20,8 @@
- [Examples Using Data References](#examples-using-data-references)
- [Dynamic ABAP Statements](#dynamic-abap-statements)
- [Dynamic ASSIGN Statements](#dynamic-assign-statements)
- [Dynamically Specifying Data Types/Creating (Data) Objects](#dynamically-specifying-data-typescreating-data-objects)
- [Creating Anonymous Data Objects by Specifying the Type Dynamically](#creating-anonymous-data-objects-by-specifying-the-type-dynamically)
- [Creating Instances of Classes by Specifying the Type Dynamically](#creating-instances-of-classes-by-specifying-the-type-dynamically)
- [Accessing Structure Components Dynamically](#accessing-structure-components-dynamically)
- [Dynamic Specifications in Statements for Processing Internal Tables](#dynamic-specifications-in-statements-for-processing-internal-tables)
- [Dynamic ABAP SQL Statements](#dynamic-abap-sql-statements)
@@ -1109,7 +1110,7 @@ ASSIGN ('ST') TO <fs>.
"Note: The typing is performed with the generic type data.
ASSIGN ('DOBJ') TO FIELD-SYMBOL(<fs_inline>).
"The statements set the sy-subrc value.
"The statements set the sy-subrc value.
ASSIGN ('DOES_NOT_EXIST') TO <fs>.
IF sy-subrc <> 0.
...
@@ -1119,9 +1120,9 @@ ENDIF.
ASSIGN dref->* TO <fs>.
"Do not use named data objects in ABAP for Cloud Development because
"you cannot know what data object you get (e.g. a class attribute or a
"local variable). If you want to assign a data object from your local
"scope, it is recommended that you specify the data objects to
"you cannot know what data object you get (e.g. a class attribute or a
"local variable). If you want to assign a data object from your local
"scope, it is recommended that you specify the data objects to
"be assigned as components of a structure. Then you can ensure that
"you assign the correct data object dynamically, using the dynamic
"component assignments as shown below.
@@ -1148,7 +1149,7 @@ DATA columnname TYPE string VALUE `COL1`.
ASSIGN st-(columnname) TO <fs>.
"Fully dynamic specification
"If the compiler can fully determine the data object in ASSIGN
"If the compiler can fully determine the data object in ASSIGN
"statements in ABAP for Cloud Development, a warning is not issued.
ASSIGN ('ST-COL1') TO <fs>.
@@ -1223,60 +1224,6 @@ ASSERT sy-subrc = 4 AND <eu> IS NOT ASSIGNED.
"------- Assigments and casting a dynamically specified type ------
"Pattern: ASSIGN ... TO <fs> CASTING TYPE (type_name).
TYPES: c1 TYPE c LENGTH 1,
c3 TYPE c LENGTH 3,
c10 TYPE c LENGTH 10,
c20 TYPE c LENGTH 20,
str TYPE string.
DATA abc TYPE c LENGTH 26 VALUE 'abcdefghijklmnopqrstuvwxyz'.
DATA(type_names) = VALUE string_table( ( `C1` ) ( `C3` ) ( `C10` ) ( `C20` ) ( `NOPE` ) ( `STR` ) ).
DATA assignment_results TYPE string_table.
FIELD-SYMBOLS <fs> TYPE clike.
LOOP AT type_names INTO DATA(type_name).
TRY.
ASSIGN abc TO <fs> CASTING TYPE (type_name).
assignment_results = VALUE #( BASE assignment_results ( |Type: '{ type_name }'; Assignment result: '{ <fs> }'| ) ).
CATCH cx_root INTO DATA(error).
assignment_results = VALUE #( BASE assignment_results
( |Error! Exception raised: { cl_abap_typedescr=>describe_by_object_ref( error )->get_relative_name( ) }; | &&
|'{ error->get_text( ) }'| ) ).
ENDTRY.
ENDLOOP.
*Content of the assignment_results table:
*Type: 'C1'; Assignment result: 'a'
*Type: 'C3'; Assignment result: 'abc'
*Type: 'C10'; Assignment result: 'abcdefghij'
*Type: 'C20'; Assignment result: 'abcdefghijklmnopqrst'
*Error! Exception raised: CX_SY_ASSIGN_CAST_UNKNOWN_TYPE; 'ASSIGN ... CASTING failed; NOPE is an unknown type'
*Error! Exception raised: CX_SY_ASSIGN_CAST_ILLEGAL_CAST; 'ASSIGN ... CASTING failed: Incompatible type'
```
> **💡 Note**<br>
> - The following `ASSIGN` statements set the `sy-subrc` value: dynamic assignments, dynamic component assignment, dynamic invokes, assignments of table expressions.
> - The return code is not set for a static assignment and an assignment of the constructor operator `CAST`.
<p align="right"><a href="#top">⬆️ back to top</a></p>
### Dynamically Specifying Data Types/Creating (Data) Objects
- For dynamic syntax elements in `CREATE OBJECT` statements, find more information [here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapcreate_object_explicit.htm) (note that parameters can be specified dynamically, too).
- In addition to character-like data objects for the type name specified in the parentheses, you can also use [absolute type names](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabsolute_typename_glosry.htm) (see the information about RTTI below).
``` abap
"Anonymous data objects are created using a type determined at
"runtime. See more information below. Note that the NEW operator
"cannot be used here.
DATA(some_type) = 'STRING'.
DATA dataref TYPE REF TO data.
CREATE DATA dataref TYPE (some_type).
CREATE DATA dataref TYPE TABLE OF (some_type).
CREATE DATA dataref TYPE REF TO (some_type).
"Using an absolute type name
CREATE DATA dataref TYPE ('\TYPE=STRING').
"Assigning a data object to a field symbol casting a dynamically
"specified type as also shown in the example above
TYPES clen5 TYPE c LENGTH 5.
@@ -1287,14 +1234,36 @@ FIELD-SYMBOLS <casttype> TYPE data.
ASSIGN dobj_c10 TO <casttype> CASTING TYPE ('CLEN5'). "12345
ASSIGN dobj_c10 TO <casttype> CASTING LIKE some_struct-('CARRID'). "123
"Dynamically creating an object as an instance of a class and
"assigning the reference to the object to an object reference
"variable. oref can be an object or interface reference variable.
"The reference variable is created here with the generic 'object'.
DATA oref_dyn TYPE REF TO object.
CREATE OBJECT oref_dyn TYPE ('ZCL_DEMO_ABAP_OBJECTS').
"Accessing an instance attribute
oref_dyn->('ANOTHER_STRING') = `hi`.
TYPES: c1 TYPE c LENGTH 1,
c3 TYPE c LENGTH 3,
c10 TYPE c LENGTH 10,
c20 TYPE c LENGTH 20,
str TYPE string.
DATA abc TYPE c LENGTH 26 VALUE 'abcdefghijklmnopqrstuvwxyz'.
DATA(type_names) = VALUE string_table( ( `C1` ) ( `C3` ) ( `C10` ) ( `C20` ) ( `NOPE` ) ( `STR` ) ).
DATA assignment_results TYPE string_table.
FIELD-SYMBOLS <clike> TYPE clike.
LOOP AT type_names INTO DATA(type_name).
TRY.
ASSIGN abc TO <clike> CASTING TYPE (type_name).
assignment_results = VALUE #( BASE assignment_results ( |Type: '{ type_name }'; Assignment result: '{ <clike> }'| ) ).
CATCH cx_root INTO DATA(error).
assignment_results = VALUE #( BASE assignment_results
( |Error! Exception raised: { cl_abap_typedescr=>describe_by_object_ref( error )->get_relative_name( ) }; | &&
|'{ error->get_text( ) }'| ) ).
ENDTRY.
ENDLOOP.
*Content of the assignment_results table:
*Type: 'C1'; Assignment result: 'a'
*Type: 'C3'; Assignment result: 'abc'
*Type: 'C10'; Assignment result: 'abcdefghij'
*Type: 'C20'; Assignment result: 'abcdefghijklmnopqrst'
*Error! Exception raised: CX_SY_ASSIGN_CAST_UNKNOWN_TYPE; 'ASSIGN ... CASTING failed; NOPE is an unknown type'
*Error! Exception raised: CX_SY_ASSIGN_CAST_ILLEGAL_CAST; 'ASSIGN ... CASTING failed: Incompatible type'
"------- Assigments and dynamic casting using a type description object ------
"Note: As covered further down and in the executable example,
"CREATE DATA and ASSIGN statements have the HANDLE addition
@@ -1303,11 +1272,105 @@ oref_dyn->('ANOTHER_STRING') = `hi`.
"Getting type description object
DATA(tdo_elem) = cl_abap_elemdescr=>get_c( 4 ).
CREATE DATA dataref TYPE HANDLE tdo_elem.
dataref->* = dobj_c10. "1234
ASSIGN dobj_c10 TO <casttype> CASTING TYPE HANDLE tdo_elem. "1234
```
> **💡 Note**<br>
> - The following `ASSIGN` statements set the `sy-subrc` value: dynamic assignments, dynamic component assignment, dynamic invokes, assignments of table expressions.
> - The return code is not set for a static assignment and an assignment of the constructor operator `CAST`.
<p align="right"><a href="#top">⬆️ back to top</a></p>
### Creating Anonymous Data Objects by Specifying the Type Dynamically
- As shown above, you create anonymous data objects using `CREATE DATA` statements and assign the reference to the data object to a reference variable.
- You can dynamically specify the type name in parentheses.
- In addition to character-like data objects (such as literals and variables) for the type name specified in the parentheses, you can also use [absolute type names](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenabsolute_typename_glosry.htm).
- You can also use type description objects and the [`TYPE HANDLE` addition](https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abapcreate_data_handle.htm) to create anonymous data objects dynamically. For this and the absolute names, find more information below in the section about RTTS.
``` abap
"------------ Specifying a type name dynamically ------------
"Anonymous data objects are created using a type determined at
"runtime. In this case, the name of the data type is specified dynamically.
"Note that the NEW operator cannot be used here.
DATA(some_type) = 'STRING'.
DATA dataref TYPE REF TO data.
"Elementary data object
CREATE DATA dataref TYPE (some_type).
"Internal tables
"Standard table with elementary line type and standard key
CREATE DATA dataref TYPE TABLE OF (some_type).
TYPES: BEGIN OF demo_struc,
comp1 TYPE c LENGTH 10,
comp2 TYPE i,
comp3 TYPE i,
END OF demo_struc.
"Structured line type, empty key specified
CREATE DATA dataref TYPE TABLE OF ('DEMO_STRUC') WITH EMPTY KEY.
"An internal table such as the following should be created by dynamically
"specifying the type and keys dynamically. The keys are specified in lines
"of an internal table with character-like line type.
DATA itab TYPE SORTED TABLE OF demo_struc WITH UNIQUE KEY comp1 comp2.
DATA(key_table) = VALUE string_table( ( `COMP1` ) ( `COMP2` ) ).
CREATE DATA dataref TYPE SORTED TABLE OF ('DEMO_STRUC') WITH UNIQUE KEY (key_table).
"Structures
CREATE DATA dataref TYPE ('DEMO_STRUC').
TYPES itab_type TYPE SORTED TABLE OF demo_struc WITH UNIQUE KEY comp1 comp2.
CREATE DATA dataref TYPE LINE OF ('ITAB_TYPE').
"Specifying data reference variables are also possible
CREATE DATA dataref TYPE REF TO (some_type).
CREATE DATA dataref TYPE REF TO ('DEMO_STRUC').
"------------ Specifying an absolute type name ------------
CREATE DATA dataref TYPE ('\TYPE=STRING').
"Getting an absolute type name; see more information further down
DATA(absolute_name) = cl_abap_typedescr=>describe_by_name( 'DEMO_STRUC' )->absolute_name.
CREATE DATA dataref TYPE (absolute_name).
"------------ HANDLE addition: Specifying a type description object ------------
"Getting a type description object. Find more information about RTTI below.
DATA(tdo_elem) = cl_abap_elemdescr=>get_c( 4 ). "type c length 4
CREATE DATA dataref TYPE HANDLE tdo_elem.
```
<p align="right"><a href="#top">⬆️ back to top</a></p>
### Creating Instances of Classes by Specifying the Type Dynamically
- [`CREATE OBJECT`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapcreate_object_explicit.htm) statements can be used to create instances of classes by specifying the type dynamically.
- It assigns the reference to the object to an object reference variable.
```abap
DATA oref_dyn TYPE REF TO object.
CREATE OBJECT oref_dyn TYPE ('ZCL_DEMO_ABAP_OBJECTS').
DATA cl TYPE string VALUE `ZCL_DEMO_ABAP_OBJECTS`.
CREATE OBJECT oref_dyn TYPE (cl).
"Note: If the class has an instance constructor specified with importing
"parameters, you can (or must in the case of non-optional parameters) pass
"actual parameters.
"This can be done either statically using the addition EXPORTING, and
"specifying the parameters statically, or by dynamically specifying the
"parameters in a parameter table. See the dynamic invoke section for
"examples on the parameter table and the static parameter passing.
"The addition EXCEPTIONS and an exception table are also available
"to handle non-class-based exceptions.
"CREATE OBJECT oref_dyn TYPE (...) EXPORTING p1 = a1 ...
"CREATE OBJECT oref_dyn TYPE (...) PARAMETER-TABLE ...
```
<p align="right"><a href="#top">⬆️ back to top</a></p>
### Accessing Structure Components Dynamically