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Field Symbols - Casting

This example demonstrates how casting with implicit and explicit type specification is carried out.

Other versions: 7.31 | 7.40 | 7.54

Source Code

    TYPES: BEGIN OF t_date,
              year  TYPE n LENGTH 4,
              month TYPE n LENGTH 2,
              day   TYPE n LENGTH 2,
           END OF t_date.

    FIELD-SYMBOLS: <fs1> TYPE t_date,
                   <fs2> TYPE any,
                   <fs3> TYPE n.

    DATA(out) = cl_demo_output=>new(
      )->write_text( |sy-datum: { sy-datum }|
      )->line( ).

<span class="blue">*------- Casting with implicit typing ------------</span>

    ASSIGN sy-datum TO <fs1> CASTING.

    out->write_text( |Year: { <fs1>-year }| ).
    out->write_text( |Month: { <fs1>-month }| ).
    out->write_text( |Day: { <fs1>-day }| ).
    out->line( ).

<span class="blue">*------- Casting with explicit typing ------------</span>

    ASSIGN sy-datum TO <fs2> CASTING TYPE t_date.

    DO.
      ASSIGN COMPONENT sy-index OF STRUCTURE <fs2> TO <fs3>.
      IF sy-subrc <> 0.
        EXIT.
      ENDIF.
      out->write_text( |Component { sy-index }: { <fs3> }| ).
    ENDDO.

    out->display( ).

Description

In the first part of the main method, an implicit casting is carried out. The field symbol <fs1> is completely typed with the local program type t_date. Using the CASTING addition of the ASSIGN statement, the field sy-datum can be treated as a structure. Without the CASTING addition assigning would not be possible, because sy-datum is not compatible with the type of the field symbol.

In the second part of the main method, an implicit casting is carried out. The field symbol <fs2> is completely generic. Using the CASTING addition of the ASSIGN statement, a cast is carried out for the field sy-datum of the local program type t_date. The field symbol <fs2> can now be treated like a structure but does not recognize components. For this reason, it must be assigned component by component to a further field symbol <fs3>.