Field Symbols

Cannot Use Field Symbols as Class Components

You cannot declare field symbols as components of classes in the declaration part of the class definition. However, you can create local field symbols within methods.

In the declaration part of the class, the following statement causes an error message::

FIELD-SYMBOLS ...

Correct syntax:

DATA ... TYPE REF TO ...
or
ALIASES ...

Cause:

The only components allowed in classes are attributes, methods, and events. Field symbols are symbolic names for other fields. They work by means of value semantics. Their role as pointers is now performed in ABAP Objects by reference variables. Their role as symbolic names has now been replaced by aliases.

No field symbols without type assignment

In ABAP Objects the addition TYPE in the statement FIELD-SYMBOLS is mandatory.

Error message in ABAP Objects if the following syntax is used:

FIELD-SYMBOLS <fs>.

Correct syntax:

FIELD-SYMBOLS <fs> TYPE ANY.

Reason:

Like method interface parameters, field symbols must alwas have explicit type assignments.

No obsolete casting withASSIGN

In ABAP Objects it is not allowed to use the additions TYPE and DECIMALS for assigning data objects to field symbols using ASSIGN.

Error message in ABAP Objects if the following syntax is used:

ASSIGN f TO <fs> TYPE ... [DECIMALS ...].

Correct syntax:

ASSIGN f TO <fs> CASTING TYPE|LIKE ...

Reason:

The TYPE and DECIMALS additions are replaced by the addition CASTING [TYPE|LIKE].

Unlike the TYPE addition, CASTING supports any kind of data types.

No Obsolete Casting forFIELD SYMBOLS

In ABAP objects the STRUCTURE addition is not allowed in the FIELD-SYMBOLS statement.

Error message in ABAP objects for:

FIELD-SYMBOLS <fs> STRUCTURE struc DEFAULT f.

Correct syntax:

FIELD-SYMBOLS <fs> TYPE|LIKE struc.

ASSIGN f TO <fs> CASTING.

Reason:

Field symbols defined with the STRUCTURE addition are a mixture of field symbols whose type is defined and a tool for casting on data types defined in the ABAP Dictionary or locally in the program. The types of field symbols are defined with the TYPE addition of the FIELD-SYMBOLS statement and the CASTING addition of the ASSIGN statement can be used for the casting.

No local copies usingASSIGN

In ABAP Objects it is not possible to use field symbols in procedures to work with copies of other data.

Error message in ABAP Objects if the following syntax is used:

ASSIGN LOCAL COPY OF INITIAL f TO <fs>.

ASSIGN LOCAL COPY OF f TO <fs>.

Correct syntax:

DATA dref TYPE REF TO data.
CREATE DATA dref LIKE f.
ASSIGN dref->* TO <fs>.

DATA dref TYPE REF TO data.
CREATE DATA dref LIKE f.
ASSIGN dref->* TO <fs>.
<fs> = f.

Reason:

Due to the introduction of the general data references concept, the addition LOCAL COPY of the statement ASSIGN is obsolete. The value of f can be copied using the assigment <fs> = f after ASSIGN.

No search limitations with dynamic ASSIGN

The search limited to table work areas of the main program in connection with the dynamic ASSIGN statement is no longer used in ABAP Objects.

Error message in ABAP Objects in the following case:

ASSIGN TABLE FIELD (<f>) TO <fs>.

Correct syntax:

ASSIGN (<f>) TO <fs>.

Cause:

Table work areas are not supported in classes.