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danrega
@@ -130,12 +130,6 @@ ASSIGN num TO <fs_gen>. "Could be any of the data objects
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"is automatically derived.
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ASSIGN num TO FIELD-SYMBOL(<fs_inl>).
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"You can also assign a particular component of a structure.
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"Second component of the structure
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ASSIGN COMPONENT 2 OF STRUCTURE struc TO <fs_gen>.
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ASSIGN COMPONENT 'CARRID' OF STRUCTURE struc TO <fs_gen>.
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"CASTING addition for matching types of data object and field symbol
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"when assigning memory areas
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TYPES c_len_3 TYPE c LENGTH 3.
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@@ -409,7 +403,7 @@ DATA(struc) = ref_carr->*.
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DATA(carrid) = ref_carr->carrid.
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ref_carr->carrid = 'UA'.
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"This syntax also works but it is less "comfortable".
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"This longer syntax with the dereferencing operator also works.
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ref_carr->*-carrname = 'United Airlines'.
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"Checking if a data reference variable can be dereferenced.
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@@ -421,6 +415,37 @@ ENDIF.
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"However, the garbage collector takes care of removing the references
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"automatically once the data is not used any more by a reference.
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CLEAR ref_carr.
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******************************************************
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"Excursion: Generic data references in older ABAP releases
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"Non-generic type
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DATA ref_int TYPE REF TO i.
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ref_int = NEW #( ).
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ref_int->* = 123.
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"Generic type
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DATA ref_generic TYPE REF TO data.
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ref_generic = NEW i( ).
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"In older ABAP releases, CREATE DATA statements were needed.
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CREATE DATA ref_generic TYPE i.
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"The only option to access the variable in older releases was via field symbols.
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ASSIGN ref_generic->* TO FIELD-SYMBOL(<fs_generic>).
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<fs_generic> = 123.
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"An access as the following, as it is possible in modern ABAP, was not possible.
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ref_generic->* = 123.
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"As shown in the example below, using dereferenced generic references is possible
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"in various places in modern ABAP.
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DATA ref_sel TYPE REF TO data.
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CREATE DATA ref_sel TYPE TABLE OF zdemo_abap_carr.
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SELECT *
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FROM zdemo_abap_carr
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INTO TABLE @ref_sel->*.
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```
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**Data references in use**
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@@ -518,44 +543,105 @@ In this context, you can usually use elementary, character-like data objects - t
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Note that dynamically specifying syntax elements has downsides, too. Consider some erroneous character-like content of such data objects. There is no syntax warning. At runtime, it can lead to runtime errors.
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- Dynamically specifying components
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- Dynamic specifications in ...
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- statements for processing internal tables
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``` abap
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"SORT statements: Sorting an internal table by dynamically specifying the component
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"Populating an internal table
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SELECT *
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FROM zdemo_abap_carr
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INTO TABLE @DATA(itab).
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``` abap
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"SORT: Dynamically specifying component name to be sorted for
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"Populating an internal table
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SELECT *
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FROM zdemo_abap_carr
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INTO TABLE @DATA(itab).
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"Dynamically specifying component name to be sorted for
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"Named data object
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DATA(field_name) = 'CARRNAME'.
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SORT itab BY (field_name).
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"Named data object
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DATA(field_name) = 'CARRNAME'.
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SORT itab BY (field_name).
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"Unnamed data object
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SORT itab BY ('CURRCODE').
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"Unnamed data object
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SORT itab BY ('CURRCODE').
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"ASSIGN statements
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"READ TABLE: Dynamically specifying keys
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READ TABLE itab INTO DATA(wa) WITH KEY (field_name) = ...
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"Declaring a field symbol
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FIELD-SYMBOLS <fs> type any.
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"MODIFY: Dynamically specifying WHERE conditions
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DATA(condition) = ( `CARRID = 'LH'` ).
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"Dynamically specifying components of structures
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ASSIGN itab[ 1 ]-('CURRCODE') to <fs>.
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MODIFY itab FROM ... TRANSPORTING ... WHERE (condition).
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DATA(struc) = itab[ 2 ].
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ASSIGN struc-(field_name) to <fs>.
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"DELETE: Dynamically specifying WHERE conditions
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DELETE itab USING KEY ... WHERE (condition).
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"Dynamically specifying components of structures that are referenced by
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"a data reference variable
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DATA(dref) = REF #( struc ).
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ASSIGN dref->('URL') to <fs>.
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"LOOP: Dynamically specifying keys
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DATA(k) = `SOME_KEY`.
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"Dynamically specifying component of a class/interface
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"In the example, the field symbol is declared inline.
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ASSIGN zdemo_abap_objects_interface=>('CONST_INTF') TO FIELD-SYMBOL(<fs_inl>).
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```
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LOOP AT itab INTO DATA(wa_lo) USING KEY (k).
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...
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ENDLOOP.
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```
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- ASSIGN statements
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``` abap
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"Accessing components of structures dynamically
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"Populating a structure
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SELECT SINGLE *
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FROM zdemo_abap_carr
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INTO @DATA(wa).
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"Declaring a field symbol
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FIELD-SYMBOLS <fs> type any.
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DATA(comp_name) = 'CARRNAME'.
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ASSIGN wa-(comp_name) TO <fs>. "named data object
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ASSIGN wa-('CARRID') TO <fs>. "unnamed data object
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"The statements set sy-subrc value. No exception occurs in case of an unsuccessful assignment.
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ASSIGN wa-('XYZ') TO <fs>.
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IF sy-subrc <> 0.
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...
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ENDIF.
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"Numeric expressions are possible. Its value is interpreted as the position
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"of the component in the structure.
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ASSIGN wa-(4) TO <fs>.
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"If the value is 0, the memory area of the entire structure is assigned to the field symbol.
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ASSIGN wa-(0) TO <fs>.
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"The statements above replace the following, older statements.
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ASSIGN COMPONENT 'CARRID' OF STRUCTURE wa TO <fs>.
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ASSIGN COMPONENT 5 OF STRUCTURE wa TO <fs>.
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"Populating a structure that is referenced by a data reference variable
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SELECT SINGLE *
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FROM zdemo_abap_carr
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INTO NEW @DATA(ref_struc).
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"Note the object component selector. The field symbol is created inline here.
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ASSIGN ref_struc->('CARRNAME') TO FIELD-SYMBOL(<fs_inl>).
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*************************************************************
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"Dynamically specifying attributes of classes/interfaces
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DATA(cl_name) = 'CL_SOME_CLASS'.
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DATA(dobj) = 'SOME_DOBJ'.
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ASSIGN cl_some_class=>(dobj) TO <fs>.
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ASSIGN (cl_name)=>some_dobj TO <fs>.
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ASSIGN (cl_name)=>(dobj) TO <fs>.
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"Class reference variable pointing to an object that contains attributes
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"and that are specified dynamically.
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DATA cl_ref TYPE REF TO cl_some_class.
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cl_ref = NEW #( ).
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ASSIGN cl_ref->('some_attribute') TO FIELD-SYMBOL(<another_fs>).
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"If ELSE UNASSIGN is specified, no memory area is assigned to the field symbol.
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"It has the state unassigned after the ASSIGN statement.
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ASSIGN cl_ref->('attr_xyz') TO FIELD-SYMBOL(<attr>) ELSE UNASSIGN.
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```
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- Dynamically specifying data types
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@@ -601,6 +687,12 @@ Note that dynamically specifying syntax elements has downsides, too. Consider so
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FROM (db_table)
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INTO TABLE @itab->*.
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"Similar to the NEW operator, you can use the addition NEW here to create an anonymous data object
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"in place. The advantage is that the data type is constructed in a suitable way.
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SELECT *
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FROM (db_table)
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INTO TABLE NEW @DATA(a_dobj).
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"Dynamic WHERE clause
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"This is an example for using an internal table with a character-like row type
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DATA(where_clause) = VALUE string_table( ( `CARRID = 'LH'` )
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