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06_Dynamic_Programming.md
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@@ -1781,23 +1781,18 @@ The type properties are represented by attributes that are accessible through th
> - For each type category (elementary type, table, and so on), there is a type description class (e.g. `CL_ABAP_STRUCTDESCR` for structures, as shown in the hierarchy tree above) that has special attributes (i.e. the properties of the respective types).
> - References to type description objects can be used, for example, after the `TYPE HANDLE` addition of the `CREATE DATA` and `ASSIGN` statements.
The following examples show the retrieval of type information. Instead of the extra declaration of data reference variables, you can use
[inline declarations](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abeninline_declaration_glosry.htm "Glossary Entry").
[Method chaining](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenmethod_chaining_glosry.htm "Glossary Entry")
comes in handy, too.
The following example explores the RTTI type hierarchy and demonstrates how to retrieve various pieces of type information using RTTI attributes and methods. You can create a demo class (adapt the class name if needed), copy and paste the code, run the class with F9 in ADT, and check the output in the console.
The example includes demo objects that are added to an internal table. This table is then looped over to retrieve type information for all objects. To retrieve a type description object, you have multiple options. One option is to use the static methods of the `cl_abap_typedescr` class, which is the root class of the RTTI hierarchy. These methods include:
The example includes demo objects that are added to an internal table. This table is then looped over to retrieve type information for all objects. To retrieve a type description object, you have multiple options. You can use the static methods of the `cl_abap_typedescr` class, which is the root class of the RTTI hierarchy. These methods include:
- `describe_by_data`: Returns an object reference in one of the classes `cl_abap_elemdescr`, `cl_abap_enumdescr`, `cl_abap_refdescr`, `cl_abap_structdescr`, or `cl_abap_tabledsecr`.
- `describe_by_object_ref`: Returns the type that an object reference variable points to.
- `describe_by_data_ref`: Returns the type that a data reference variable points to.
- `describe_by_name`: Returns a type description object when providing the relative or absolute name of a type.
Notes:
- The `*_ref` methods return objects of the dynamic type.
- In the bigger example of the demo class, we do not use type names, but rather objects (`describe_by_name` is used in the smaller example in the demo class). Therefore, we first try to get a type description object using the `describe_by_object_ref` method to obtain an instance of `cl_abap_objectdescr`. If this fails, it means we have an instance of `cl_abap_datadescr`, which is the next subclass in the hierarchy. We can retrieve this using the `describe_by_data` method.
- The `describe_by_data` method also works for references, including object/interface reference variables. In these cases, the returned object points to `cl_abap_refdescr`. We can then use the `get_referenced_type` method to obtain more details about the actual reference.
- In the bigger example of the demo class (the first `LOOP` statement), type names are not used, but rather objects. First, an attempt is made to get a type description object using the `describe_by_object_ref` method to obtain an instance of `cl_abap_objectdescr`. If this fails, it means it is an instance of `cl_abap_datadescr`, which is the next subclass in the hierarchy. It can be retrieved using the `describe_by_data` method. `describe_by_name` is used in the smaller example in the demo class (the second `LOOP` statement).
- The `describe_by_data` method also works for references, including object/interface reference variables. In these cases, the returned object points to `cl_abap_refdescr`. The `get_referenced_type` method can then be used to obtain more details about the actual reference.
- The example also demonstrates the dynamic creation of data objects using the retrieved type description objects and the `HANDLE` addition to the `CREATE DATA` statement. It also shows dynamic creations using the dynamic specification of the type and the absolute name. The latter is also possible with the `CREATE OBJECT` statement to create objects dynamically. In ABAP for Cloud Development, absolute names having the pattern `\TYPE=%_...` (an internal technical name that is available for [bound data types](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenbound_data_type_glosry.htm)) cannot be used for the dynamic creation.
- To visualize the retrieved information, many values are added to a string table. Note that this example is tailored to cover all subclasses of the RTTI hierarchy, but it does not explore all available options for information retrieval.
- The example uses artifacts from the ABAP cheat sheet repository.
@@ -1830,7 +1825,7 @@ CLASS zcl_some_class IMPLEMENTATION.
"Elementary type
DATA elem_dobj TYPE c LENGTH 4 VALUE 'ABAP'.
"Enumeration type
"Enumerated type
TYPES: BEGIN OF ENUM enum_t,
enum1,
enum2,
@@ -1947,18 +1942,18 @@ CLASS zcl_some_class IMPLEMENTATION.
IF tdo IS INSTANCE OF cl_abap_elemdescr.
INSERT |{ tabix } Is instance of cl_abap_elemdescr| INTO TABLE str_tab.
"Enumeration types
"Enumerated types
IF tdo IS INSTANCE OF cl_abap_enumdescr.
INSERT |{ tabix } Is instance of cl_abap_enumdescr| INTO TABLE str_tab.
DATA(enum) = CAST cl_abap_enumdescr( tdo ).
"Various type-specific information retrieval
"Base type of enumeration type
"Base type of enumerated type
DATA(enum_base_type_kind) = enum->base_type_kind.
INSERT |{ tabix } Base type: { enum_base_type_kind }| INTO TABLE str_tab.
"Elements of the enumeration type
"Elements of the enumerated type
DATA(enum_elements) = enum->members.
INSERT |{ tabix } Elements:| &&
| { REDUCE string( INIT str = `` FOR <l> IN enum_elements NEXT str = |{ str }{ COND #( WHEN str IS NOT INITIAL THEN ` / ` ) }| &&
@@ -1988,7 +1983,7 @@ CLASS zcl_some_class IMPLEMENTATION.
INSERT |{ tabix } Dynamic data object creation error: { err_enum->get_text( ) }| INTO TABLE str_tab.
ENDTRY.
"Elementary types other than enumeration types
"Elementary types other than enumerated types
ELSE.
DATA(elem) = CAST cl_abap_elemdescr( tdo ).
@@ -2111,8 +2106,7 @@ CLASS zcl_some_class IMPLEMENTATION.
DATA(struc_components) = struc->components.
INSERT |{ tabix } Components 1: | &&
|{ REDUCE string( INIT str = `` FOR <comp1> IN struc_components NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN ` / ` ) }{ <comp1>-name } ({ <comp1>-type_kind })| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN str IS NOT INITIAL THEN ` / ` ) }{ <comp1>-name } ({ <comp1>-type_kind })| ) }| INTO TABLE str_tab.
"Structure components (more details)
"The following method also returns a table with component information. In this case,
@@ -2121,8 +2115,7 @@ CLASS zcl_some_class IMPLEMENTATION.
DATA(struc_components_tab) = struc->get_components( ).
INSERT |{ tabix } Components 2: | &&
|{ REDUCE string( INIT str = `` FOR <comp2> IN struc_components_tab NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN ` / ` ) }{ <comp2>-name } ({ <comp2>-type->type_kind })| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN str IS NOT INITIAL THEN ` / ` ) }{ <comp2>-name } ({ <comp2>-type->type_kind })| ) }| INTO TABLE str_tab.
"Checking if the structure has includes
DATA(struc_has_include) = struc->has_include.
@@ -2133,16 +2126,14 @@ CLASS zcl_some_class IMPLEMENTATION.
DATA(struc_incl_view) = struc->get_included_view( ).
INSERT |{ tabix } Included view: | &&
|{ REDUCE string( INIT str = `` FOR <comp3> IN struc_incl_view NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <comp3>-name }| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <comp3>-name }| ) }| INTO TABLE str_tab.
"Returning component names of all components and substructures in included
"structures that contain included structures
DATA(struc_all_incl) = struc->get_symbols( ).
INSERT |{ tabix } Included view: | &&
|{ REDUCE string( INIT str = `` FOR <comp4> IN struc_all_incl NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <comp4>-name }| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <comp4>-name }| ) }| INTO TABLE str_tab.
ENDIF.
"Checking the type compatibility of the data object
@@ -2203,8 +2194,7 @@ CLASS zcl_some_class IMPLEMENTATION.
INSERT |{ tabix } Table keys: { REDUCE string( INIT str = `` FOR <key2> IN tab_keys NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ REDUCE string( INIT str2 = `` FOR <key3> IN <key2>-components NEXT str2 = |{ str2 }| &&
|{ COND #( WHEN str2 IS NOT INITIAL THEN `/` ) }{ <key3>-name }| ) } (is primary: "{ <key2>-is_primary }", | &&
|is unique: "{ <key2>-is_unique }", key kind: "{ <key2>-key_kind }", access kind: "{ <key2>-access_kind }")| ) }|
INTO TABLE str_tab.
|is unique: "{ <key2>-is_unique }", key kind: "{ <key2>-key_kind }", access kind: "{ <key2>-access_kind }")| ) }| INTO TABLE str_tab.
DATA(tab_keys_aliases) = tab->get_key_aliases( ).
IF tab_keys_aliases IS NOT INITIAL.
@@ -2292,8 +2282,7 @@ CLASS zcl_some_class IMPLEMENTATION.
DATA(obj_ref_attributes) = obj_ref->attributes.
INSERT |{ tabix } Attributes: { REDUCE string( INIT str = `` FOR <attr> IN obj_ref_attributes NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <attr>-name } (vis: "{ <attr>-visibility }", static: "{ <attr>-is_class }")| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN str IS NOT INITIAL THEN `, ` ) }{ <attr>-name } (vis: "{ <attr>-visibility }", static: "{ <attr>-is_class }")| ) }| INTO TABLE str_tab.
"Getting the interfaces implemented
DATA(obj_ref_interfaces) = obj_ref->interfaces.
@@ -2341,8 +2330,7 @@ CLASS zcl_some_class IMPLEMENTATION.
IF absolute_name CS '\CLASS=ZCL_DEMO_ABAP_OBJECTS' AND err_obj IS INITIAL.
INSERT |{ tabix } Dynamic attribute access: { REDUCE string( INIT str = `` FOR <m> IN obj_ref_attributes NEXT str = |{ str }| &&
|{ COND #( WHEN str IS NOT INITIAL AND <m>-visibility = 'U' THEN ` / ` ) }| &&
|{ COND #( WHEN <m>-visibility = 'U' THEN <m>-name && ` ("` && CONV string( dyn_obj->(<m>-name) ) && `")` ) }| ) }|
INTO TABLE str_tab.
|{ COND #( WHEN <m>-visibility = 'U' THEN <m>-name && ` ("` && CONV string( dyn_obj->(<m>-name) ) && `")` ) }| ) }| INTO TABLE str_tab.
ENDIF.
"-----------------------------------------------------------------------
@@ -2456,7 +2444,7 @@ CLASS zcl_some_class IMPLEMENTATION.
"Elementary type
TYPES packed TYPE p LENGTH 8 DECIMALS 2.
"Enumeration type
"Enumerated type
TYPES: BEGIN OF ENUM enum_type,
enum_a,
enum_b,
@@ -2474,7 +2462,9 @@ CLASS zcl_some_class IMPLEMENTATION.
"Internal table types
TYPES int_tab_type TYPE TABLE OF i WITH EMPTY KEY.
TYPES sorted_tab_type TYPE SORTED TABLE OF flat_struc_type WITH UNIQUE KEY a WITH NON-UNIQUE SORTED KEY sec_key ALIAS sk COMPONENTS b c.
TYPES sorted_tab_type TYPE SORTED TABLE OF flat_struc_type
WITH UNIQUE KEY a
WITH NON-UNIQUE SORTED KEY sec_key ALIAS sk COMPONENTS b c.
TYPES itab_der_type TYPE TABLE FOR UPDATE zdemo_abap_rap_ro_m.
"Reference types
@@ -2482,20 +2472,20 @@ CLASS zcl_some_class IMPLEMENTATION.
TYPES gen_dref_type TYPE REF TO data.
"Class and interface names are specified directly
DATA(type_names) = VALUE string_table( ( `PACKED` ) "Elementary type (1)
( `TIMESTAMPL` ) "Elementary type, global DDIC type/data element (2)
( `ENUM_TYPE` ) "Enumeration type (3)
( `FLAT_STRUC_TYPE` ) "Structured type, flat structure (4)
( `STR_DER_TYPE` ) "Structured type, BDEF derived type (5)
( `INT_TAB_TYPE` ) "Table type, elementary line type (6)
( `SORTED_TAB_TYPE` ) "Table type, structured line type (7)
( `ITAB_DER_TYPE` ) "Table type, BDEF derived type (8)
( `INT_DREF_TYPE` ) "Reference type (9)
( `GEN_DREF_TYPE` ) "Reference type, generic type (10)
( `CL_ABAP_TYPEDESCR` ) "Class name (11)
( `CL_ABAP_CORRESPONDING` ) "Class name (12)
( `IF_OO_ADT_CLASSRUN` ) "Interface name (13)
( `ZDEMO_ABAP_OBJECTS_INTERFACE` ) "Interface name (14)
DATA(type_names) = VALUE string_table( ( `PACKED` ) "Elementary type (1)
( `TIMESTAMPL` ) "Elementary type, global DDIC type/data element (2)
( `ENUM_TYPE` ) "Enumerated type (3)
( `FLAT_STRUC_TYPE` ) "Structured type, flat structure (4)
( `STR_DER_TYPE` ) "Structured type, BDEF derived type (5)
( `INT_TAB_TYPE` ) "Table type, elementary line type (6)
( `SORTED_TAB_TYPE` ) "Table type, structured line type (7)
( `ITAB_DER_TYPE` ) "Table type, BDEF derived type (8)
( `INT_DREF_TYPE` ) "Reference type (9)
( `GEN_DREF_TYPE` ) "Reference type, generic type (10)
( `CL_ABAP_TYPEDESCR` ) "Class name (11)
( `CL_ABAP_CORRESPONDING` ) "Class name (12)
( `IF_OO_ADT_CLASSRUN` ) "Interface name (13)
( `ZDEMO_ABAP_OBJECTS_INTERFACE` ) "Interface name (14)
).
LOOP AT type_names INTO DATA(type_name).
@@ -2542,7 +2532,8 @@ ENDCLASS.
#### Excursion: Inline Declaration, CAST Operator, Method Chaining
As shown in the example above, you can use inline declaration, the `CAST` operator for casting, and method chaining to write more concise code and avoid declaring helper variables. However, also consider the code's debuggability, maintainability, and readability.
As shown in the example above, you can use [inline declarations](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abeninline_declaration_glosry.htm "Glossary Entry"), the [`CAST`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenconstructor_expression_cast.htm) operator for casting, and [method chaining](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenmethod_chaining_glosry.htm "Glossary Entry") to write more concise code and avoid declaring helper variables. However, also consider the code's debuggability, maintainability, and readability.
```abap
DATA some_struc TYPE zdemo_abap_carr.