Declaring Field Symbols in a work area
Hi all!
I'm triying to learn the use of FieldSymbols, and I wrote in my code this:
REPORT zpractica01.
Types
TYPES: BEGIN OF ty_tabla,
name(25) TYPE c,
address(60) TYPE c,
monto(3) TYPE p decimals 2,
END OF ty_tabla.
Internal Table
DATA: t_tabla TYPE STANDARD TABLE OF ty_tabla.
*Work Area
DATA: vl_variable TYPE c LENGTH 512.
Field Symbols
FIELD-SYMBOLS <linea> STRUCTURE st_tabla DEFAULT vl_variable.
If I try to activate the code I see this error:
In the Unicode context, the structure <LINEA> typed using STRUCTURE can only contain character-type components (type C,N,D,T).
I can see that the problem begins when I use a type P inside the structure, but I need to have a type P, so I would like to know how can i use it.
Could you please teach me how I should declare my field symbols in order to use as an structure with a type P field within a loop at - endloop?
I'll really appreciate your help.
Best regards!
Gaby
Edited by: gpsoria on Aug 24, 2009 4:30 PM
Hello Gaby,
You are getting the error because the structure st_tabla & variable vl_variable are not mutually convertible in a Unicode environment.
Just change the definition of vl_variable & you code will activate.
REPORT zpractica01.
* Types
TYPES: BEGIN OF ty_tabla,
name(25) TYPE c,
address(60) TYPE c,
monto(3) TYPE p decimals 2,
END OF ty_tabla.
* Internal Table
DATA: t_tabla TYPE STANDARD TABLE OF ty_tabla.
*Work Area
DATA: st_tabla TYPE ty_tabla. "--> Add this line
DATA: vl_variable TYPE ty_tabla. "c LENGTH 512.
* Field Symbols
FIELD-SYMBOLS <linea> STRUCTURE st_tabla DEFAULT vl_variable.
*I will suggest decalre like this:
FIELD-SYMBOLS <linea1> TYPE ty_tabla.
Hope i am clear.
BR,
Suhas
Similar Messages
-
Right way to declare field symbols
i am new to field symbols, pls help
i want to know which is the right way of declaration ?
types: begin of typ_tab,
vbeln type vbap-vbeln,
posnr type vbap-posnr,
matnr type vbap-matnr,
end of typ_tab.
data: itab type standard table of typ_tab,
wa type typ_tab.
field-symbols: <f_t> type standard table,
<f_w> type any, or <f_w> like line of typ_tab, ??
<f_s> type any.
select vbeln posnr ....... into itab......
assign itab to <f_t>.
assign wa to <f_w>.
loop at <f_t> assigning <f_w>.
assign component 'vbeln' of structure <f_w> to <f_s>.
write : / <f_s>.
endloop.
OR
loop at itab assigning <f_w>.
write: / <f_w>-vbeln.
endloop.
r these 2 statements correctt ? if so then which one to use, pls show with an example. wats the diff btwn above 2 types of looping statements ? how to use read statement on this ?Hello Saurajit,
Both the way are correct. And it depends on the requirement, which one to use.
<f_w> TYPE ty_tab - is TYPED field symbol - if you know TYPE before runtime you can use this. It will just work like a static work area.
<f_w> TYPE any - is not TYPED and structure of this field symbol is defined during runtime using ASSIGN statement. And fields of the structure is read by ASSIGN COMPONENT <<field name>> statement. -
Declaring Field Symbols in Public Section of class
Dear All,
I am working with class and hav declared some field symbols in one of the method.
Now I want to move these declaration in Public section of the class so that this field symbol declaration can be used by other methods of the class but I am not able to do the same.
Can anyone help me in finding as what I am doing wrong here.
Regards,
Lalit KabraWhat you are trying to do is define an attribute. I doubt you can use field symbol as a class attribute. Consider using a data object instead.
Data : dref type ref to data.
This can later be deferenced in the individual methods.
Hope this helps.
Here's an example for the same:
REPORT z_class_001 .
* CLASS lcl_class1 DEFINITION
CLASS lcl_class1 DEFINITION.
PUBLIC SECTION.
DATA dref TYPE REF TO data.
METHODS : constructor IMPORTING i_type TYPE char20,
meth1 IMPORTING value TYPE i.
ENDCLASS. "lcl_class1 DEFINITION
* CLASS lcl_class1 IMPLEMENTATION
CLASS lcl_class1 IMPLEMENTATION.
METHOD constructor.
CREATE DATA dref TYPE (i_type).
ENDMETHOD. "constructor
METHOD meth1.
FIELD-SYMBOLS <fs> TYPE ANY.
ASSIGN dref->* TO <fs>.
WRITE: 'Value is ' ,value.
ASSIGN value TO <fs>.
WRITE: 'Field symbol is ', <fs>.
ENDMETHOD. "meth1
ENDCLASS. "lcl_class1 IMPLEMENTATION
START-OF-SELECTION.
DATA ref_class TYPE REF TO lcl_class1.
CREATE OBJECT ref_class EXPORTING i_type = 'I'.
CALL METHOD ref_class->meth1
EXPORTING
value = 3.
BR,
Advait
Edited by: Advait Gode on Sep 16, 2009 9:44 AM -
Difference between Field symbols and work area for Internal tables
Hi,
In ECC versions we all know that we need to declare the internal tables without headerline, and for handling the internal tables we need to use exclusive work areas.
Currently i have an issue that we have been asked to use field symbols instead of work areas...can any one help me how to use the field symbols and also let me know how it will improve the performance of the program..
Thanks and Regards,
KathirHi
DATA: WA TYPE ITAB.
LOOP AT ITAB INTO WA.
IF WA-FIELD = .....
ENDIF.
ENDLOOP.[(code]
FIELD-SYMBOLS <WA> TYPE ANY.
LOOP AT ITAB ASSIGNING <WA>.
ENDLOOP.
Now the problem is you can't know the name of the fields of the table at runtime, so you can't write:
IF <WA>-FIELD = .....
ENDIF.
Anyway you can create a field-symbols strcturated like the table:
[code]FIELD-SYMBOLS <WA> TYPE ITAB.
LOOP AT ITAB ASSIGNING <WA>.
IF <WA>-FIELD = .....
ENDIF.
ENDLOOP.
I don't know which are the differences for the performance between to use a field-symbol and to use a structure as work-area.
The differnce between the field-symbols and work-area is the field-symbol is assigned directly to the record, so u don't need to do a MODIFY statament to change something:
LOOP AT ITAB INTO WA.
WA-FIELD =
MODIFY ITAB FROM WA.
ENDLOOP.
LOOP AT ITAB ASSIGNING <WA>.
<WA>-FIELD =
ENDLOOP.
These two pieces of abap code do the same action, so probably the field-symbol improve the performance because it do an access directly to the record without to use an external structure as workarea.
Max -
Performance Field Symbols Vs Work Area
Hi,
I want to some operations (Validations and Calculations) form each entry of internal table.
Which is better way to access the data in internal table either using field symbol or using work area?
I heard that using filed symbols is performance issue. May I know in which cases we should not use field symbols?
Regards,
KumarI do not think, the runtime creates a pointer to each line of the itab.
The developer creates ONE fieldsymbol ( for a loop for example ) --> a pointer, which is iteratively assigned, pointing to only one line at one time.
With the usage itself it seems to offer a benefit, which isn't really one, If You only read data.
People might say, You can omit a clear, if working with fieldsymbols.
But You have to add a check for sy-subrc, or You will suffer from a dump, which usually never happens, if working with work areas the same way, like fieldsymbols.
The real benefit only comes into play, if You want to modify the data in the internal table, because You are already acting on the line of the table (pointer to record n ), what allows You, to omit any modify to transfer changed values back to the internal table.
In terms of performance I must see it technically and I hope, someone can confirm/reject my statement, so that I (if I was wrong) could keep that in mind.
A fieldsymbol (lets talk about them in technical way, as a pointer) is in fact a variable, which holds an address of another variable( which itself also can hold an address and so on).
Pointers are either 4 byte or 8 byte. So, it does not matter, how much columns Your internal table has, technically the fieldsymbol is either 4 byte big or 8 byte big. And exactly this amount is used in the ram of the application server.
In fact pointers even do not have a type, as usual pointers are always integer.
A workarea is a linear, continous allocation of memory space, exacly matching the data-structure, which is used for declaration. So it is obvious, that this workarea uses much more memory of the ram, as long their elements exceed 4 / 8 bytes.
Still then it is not more performant, because changed data of a workarea has to be transferred to the internal table, (mostly, if one wants to modify), but with field-symbols this step is removed.
So in fact there are two technical reasons for using field-symbols.
One is, You save memory-space and the second is, You save the transferring.
In an even deeper way, one can say, that , by design, a cpu with its address bus is just intended to understand addresses best ( directly after 0 and 1 and hex ). -
Hi SDN's
I have createad dynamic internal table using the method cl_alv_table_create=>create_dynamic_table from the blog
/people/rich.heilman2/blog/2005/07/27/dynamic-internal-tables-and-structures--abap
i am struck at the last point. what i wanted to know is the the internal table is in the form of a Field Symbol <FS> . But i have an internal table which already contains the data.. how do i move the data from internal tables to the Dynamic internal table.. I had already posted previously, but not able to understand .. can some body help me in understanding to get the data from Internal table to the dynamic internal table
<b>My internal table</b> is in the below format
Alloc no|ChargeCode |Amount |
A119 |301 |100 |
A119 |301 |200 |
A119 |302 |150 |
A119 |302 |250 |
A119 |303 |100 |
A229 |301 |100 |
A229 |321 |100 |
A239 |301 |100 |
A239 |303 |50 |
and i have the <b>dynaic internal table</b> format as below
Alloc No|301 |302 |303 |321 |
A119 |300 |400 |100 |NIL |
A229 |100 |NIL |NIL |100 |
A239 |100 |NIL |50 |NIL |
Please help me in understanding to move the data in to the above formatHi Pratyu Usha,
I started dealing with it recently, so I'll try to help...
I built the dynamic table row after row.
To do this efficiently, the static (non-dynamic) table must be sorted by "Alloc No".
Then you need a field-symbol for the work-area line of the dynamic table:
ASSIGN LOCAL COPY OF INITIAL LINE OF <dynamic-table> TO <line>.
where <dynamic-table> is the field-symbol representing your dynamic table.
then you loop at your static table, and for each line of the static table you assign the right column of the dynamic table's line to other field-symbol:
ASSIGN COMPONENT StaticTable-ChargeCode OF STRUCTURE <line> TO <field>.
where <field> is another field-symbol and StaticTable is your static table...
For example, suppose that you're currently in the first row of your static table - <field> will point to the column named "301" of the work-area of your dynamic table.
now you just put the value inside that column:
<field> = StaticTable-Amount.
OR if you want to sum the value:
ADD StaticTable-Amount to <field>.
Now, at end of "Alloc no", you need to add your dynamic work-area to the dynamic table:
APPEND <line> TO <dynamic-table>.
CLEAR: <line>.
There.
That should work.
Please let me know!
Alon -
Declare work area of type = standard table
Hi All,
How to declare a workarea of type standard table in ABAP Objects..
the syntax check of ABAP Objects showing error for the general ABAP Code
for the same..
Thanks in Advance, Sudeep..Hi Sudeep,
I had shown the declarations for internal table and work area as well
if you just want work area
just use the second statement
data : is_vbak type vbak. " work area of VBAK
Regards
Gopi -
The difference between FIELD-SYMBOL and normal DATA TYPE
Dear experts,
Please see the example below, both are output the same result.
DATA: EXTERNAL_RECORD(4000),
POSITION TYPE I,
LENGTH TYPE N,
ENTRY TYPE STRING.
EXTERNAL_RECORD = '0005Smith0007Edwards0005Young'.
DO.
LENGTH = EXTERNAL_RECORD+POSITION(4).
IF LENGTH = 0.
EXIT.
ENDIF.
ADD 4 TO POSITION.
MOVE EXTERNAL_RECORD+POSITION(LENGTH) TO ENTRY.
WRITE ENTRY.
ADD LENGTH TO POSITION.
IF POSITION >= 4000.
EXIT.
ENDIF.
ENDDO.
--OR It can be written as--
DATA: EXTERNAL_RECORD(4000),
POSITION TYPE I,
LENGTH TYPE N.
FIELD-SYMBOLS <ENTRY>.
EXTERNAL_RECORD = '0005Smith0007Edwards0005Young'.
DO.
LENGTH = EXTERNAL_RECORD+POSITION(4).
IF LENGTH = 0.
EXIT.
ENDIF.
ADD 4 TO POSITION.
ASSIGN EXTERNAL_RECORD+POSITION(LENGTH) TO <ENTRY>.
WRITE <ENTRY>.
ADD LENGTH TO POSITION.
IF POSITION >= 4000.
EXIT.
ENDIF.
ENDDO.
Is there any special circumstances we need to use FIELD-SYMBOL?
Why is FIELD-SYMBOL is introduce in the first place?
Kindly advice with example.
Thanks in advance for those who can help me on this.HI,
You can use field symbols to make the program more dynamic. In this example the name of a table control is substituted by a field symbol. Thus you cal call the form with any internal table, using the name of the table control as a parameter.
Example
form insert_row
using p_tc_name.
field-symbols <tc> type cxtab_control. "Table control
assign (p_tc_name) to <tc>.
insert 100 lines in table control
<tc>-lines = 100.
Field symbols allow you to:
** Assign an alias to a data object(for example, a shortened
name for data objects structured through several hierarchies
- <fs>-f instead of rec1-rec2-rec3-f)
** Set the offset and length for a string variably at runtime
** Set a pointer to a data object that you determine at runtime (dynamic ASSIGN)
** Adopt or change the type of a field dynamically at runtime
** Access components of a structure
** (from Release 4.5A) Point to lines of an internal table
(process internal tables without a separate work area)
Field symbols in ABAP are similar to pointers in other programming
languages. However, pointers (as used in PASCAL or C) differ from ABAP
field symbols in their reference syntax.
The statement ASSIGN f to <fs> assigns the field f to field
symbol <fs>. The field symbol <fs> then "points" to the
contents of field f at runtime. This means that all changes to the
contents of f are visible in <fs> and vice versa. You declare
the field symbol <fs> using the statement FIELD-SYMBOLS: <fs>.
Reference syntax
Programming languages such as PASCAL and C use a dereferencing symbol
to indicate the difference between a reference and the object to which
it refers; so PASCAL would use p^ for a pointer instead of p, C would
use *p instead of p. ABAP does not have any such dereferencing symbol.
** In PASCAL or C, if you assign a pointer p1 to a pointer p2,
you force p1 to point to the object to which p2 refers (reference semantics).
** In ABAP, if you assign a field symbol <fs1> to a field
symbol <fs2>, <fs1> takes the value of the data object to
which <fs2> refers (value semantics).
** Field symbols in ABAP are always dereferenced, that is,
they always access the referenced data object. If you want to
change the reference yourself in ABAP, you can use the ASSIGN statement
to assign field symbol <fs1> to field symbol <fs2>.
Using field symbols
You declare field symbols using the FIELD-SYMBOLS statement.
They may be declared either with or without a specific type.
At runtime you assign a field to the field symbol using the ASSIGN
statement. All of the operations on the field symbol act on the field
assigned to it.
When you assign a field to an untyped field symbol, the field symbol
adopts the type of the field. If, on the other hand, you want to assign
a field to a typed field symbol, the type of the field and that of the
field symbol must be compatible.
A field symbol can point to any data object and from Release 4.5A,
they can also point to lines of internal tables.
The brackets (<>) are part of the syntax.
Use the expression <fs> IS ASSIGNED to find out whether the field
symbol <fs> is assigned to a field.
The statement UNASSIGN <fs> sets the field symbol <fs> so
that it points to nothing. The logical expression <fs>
IS ASSIGNED is then false. The corresponding negative expression
is IF NOT <fs> IS ASSIGNED.
An unassigned field symbol <fs> behaves as a constant with
type C(1) and initial value SPACE.
MOVE <fs>
TO dest Transfers the initial value SPACE to the variable dest
MOVE 'A' to <fs>
Not possible, since <fs> is a constant
(runtime error).
To lift a type restriction, use the CASTING addition in the
ASSIGN statement. The data object is then interpreted as though
it had the data type of the field symbol. You can also do this
with untyped field symbols using the CASTING TYPE <type> addition.
The danger with pointers is that they may point to invalid areas.
This danger is not so acute in ABAP, because the language does not
use address arithmetic (for example, in other languages, pointer p
might point to address 1024. After the statement p = p + 10, it would
point to the address 1034). However, the danger does still exist, and
memory protection violations lead to runtime errors.
A pointer in ABAP may not point beyond a segment boundary. ABAP does
not have one large address space, but rather a set of segments.
Each of the following has its own segment:
* All global data
* All local data
* Each table work area (TABLES)
* Each COMMON PART
You should only let field symbols move within an elementary field or
structure where ABAP allows you to assign both within the global data
and beyond a field boundary.
Rgds
Umakanth -
Field Symbols, Field String, and Field Group.
Hi,
Can you differentiate between filed symbols, field strings and field groups,
With regards,
Bharath Mohan BHi,
Field Symbols
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects.
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve performance in some cases.
check the below links u will get the answers for your questions
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
http://www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/field_sy.htm
http://searchsap.techtarget.com/tip/1,289483,sid21_gci920484,00.html
Syntax Diagram
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Extras:
1. ... TYPE type
2. ... TYPE REF TO cif
3. ... TYPE REF TO DATA
4. ... TYPE LINE OF type
5. ... LIKE s
6. ... LIKE LINE OF s
7. ... TYPE tabkind
8. ... STRUCTURE s DEFAULT wa
The syntax check performed in an ABAP Objects context is stricter than in other ABAP areas. See Cannot Use Untyped Field Symbols ad Cannot Use Field Symbols as Components of Classes.
Effect
This statement declares a symbolic field called <fs>. At runtime, you can assign a concrete field to the field symbol using ASSIGN. All operations performed with the field symbol then directly affect the field assigned to it.
You can only use one of the additions.
Example
Output aircraft type from the table SFLIGHT using a field symbol:
FIELD-SYMBOLS <PT> TYPE ANY.
DATA SFLIGHT_WA TYPE SFLIGHT.
ASSIGN SFLIGHT_WA-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... TYPE type
Addition 2
... TYPE REF TO cif
Addition 3
... TYPE REF TO DATA
Addition 4
... TYPE LINE OF type
Addition 5
... LIKE s
Addition 6
... LIKE LINE OF s
Addition 7
... TYPE tabkind
Effect
You can define the type of the field symbol using additions 2 to 7 (just as you can for FORM parameters (compare Defining the Type of Subroutine Parameters). When you use the ASSIGN statement, the system carries out the same type checks as for USING parameters of FORMs.
This addition is not allowed in an ABAP Objects context. See Cannot Use Obsolete Casting for FIELD SYMBOLS.
In some cases, the syntax rules that apply to Unicode programs are different than those for non-Unicode programs. See Defining Types Using STRUCTURE.
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP Dictionary (s). All fields of the structure can be addressed by name: <fs>-fieldname. The structured field symbol points initially to the work area wa specified after DEFAULT.
The work area wa must be at least as long as the structure s. If s contains fields of the type I or F, wa should have the structure s or at least begin in that way, since otherwise alignment problems may occur.
Example
Address components of the flight bookings table SBOOK using a field symbol:
DATA SBOOK_WA LIKE SBOOK.
FIELD-SYMBOLS <SB> STRUCTURE SBOOK
DEFAULT SBOOK_WA.
WRITE: <SB>-BOOKID, <SB>-FLDATE.
Related
ASSIGN, DATA
Additional help
Declaring Field Symbols
FIELD GROUPS
are used to hold/handle large amount of data when the internal table are not useful
we use EXTRACT statement, HEADER structure in them
see the example
REPORT demo_extract.
NODES: spfli, sflight.
FIELD-GROUPS: header, flight_info, flight_date.
START-OF-SELECTION.
INSERT: spfli-carrid spfli-connid sflight-fldate
INTO header,
spfli-cityfrom spfli-cityto
INTO flight_info.
GET spfli.
EXTRACT flight_info.
GET sflight.
EXTRACT flight_date.
END-OF-SELECTION.
SORT STABLE.
LOOP.
AT FIRST.
WRITE / 'Flight list'.
ULINE.
ENDAT.
AT flight_info WITH flight_date.
WRITE: / spfli-carrid , spfli-connid, sflight-fldate,
spfli-cityfrom, spfli-cityto.
ENDAT.
AT flight_date.
WRITE: / spfli-carrid , spfli-connid, sflight-fldate.
ENDAT.
AT LAST.
ULINE.
WRITE: cnt(spfli-carrid), 'Airlines'.
ULINE.
ENDAT.
ENDLOOP.
FIELD STRING is nothing but a string with one row of records.
Reward points if useful
regards
Anji -
Re: field symbols and interna table
hi,
here is field symbol which is table type
FIELD-SYMBOLS: <gt_pos_data> TYPE table.
there is one internal table it_data.
how can move <gt_pos_data> to it_data.
please help me.
rgdsHi
You can assign field wise:
like
<gt_pos_data>- field to to it_data-field.
Field Symbols
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects.
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve performance in some cases.
check the below links u will get the answers for your questions
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
http://www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/field_sy.htm
http://searchsap.techtarget.com/tip/1,289483,sid21_gci920484,00.html
Syntax Diagram
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Extras:
1. ... TYPE type
2. ... TYPE REF TO cif
3. ... TYPE REF TO DATA
4. ... TYPE LINE OF type
5. ... LIKE s
6. ... LIKE LINE OF s
7. ... TYPE tabkind
8. ... STRUCTURE s DEFAULT wa
The syntax check performed in an ABAP Objects context is stricter than in other ABAP areas. See Cannot Use Untyped Field Symbols ad Cannot Use Field Symbols as Components of Classes.
Effect
This statement declares a symbolic field called <fs>. At runtime, you can assign a concrete field to the field symbol using ASSIGN. All operations performed with the field symbol then directly affect the field assigned to it.
You can only use one of the additions.
Example
Output aircraft type from the table SFLIGHT using a field symbol:
FIELD-SYMBOLS <PT> TYPE ANY.
DATA SFLIGHT_WA TYPE SFLIGHT.
ASSIGN SFLIGHT_WA-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... TYPE type
Addition 2
... TYPE REF TO cif
Addition 3
... TYPE REF TO DATA
Addition 4
... TYPE LINE OF type
Addition 5
... LIKE s
Addition 6
... LIKE LINE OF s
Addition 7
... TYPE tabkind
Effect
You can define the type of the field symbol using additions 2 to 7 (just as you can for FORM parameters (compare Defining the Type of Subroutine Parameters). When you use the ASSIGN statement, the system carries out the same type checks as for USING parameters of FORMs.
This addition is not allowed in an ABAP Objects context. See Cannot Use Obsolete Casting for FIELD SYMBOLS.
In some cases, the syntax rules that apply to Unicode programs are different than those for non-Unicode programs. See Defining Types Using STRUCTURE.
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP Dictionary (s). All fields of the structure can be addressed by name: <fs>-fieldname. The structured field symbol points initially to the work area wa specified after DEFAULT.
The work area wa must be at least as long as the structure s. If s contains fields of the type I or F, wa should have the structure s or at least begin in that way, since otherwise alignment problems may occur.
Example
Address components of the flight bookings table SBOOK using a field symbol:
DATA SBOOK_WA LIKE SBOOK.
FIELD-SYMBOLS <SB> STRUCTURE SBOOK
DEFAULT SBOOK_WA.
WRITE: <SB>-BOOKID, <SB>-FLDATE.
Related
ASSIGN, DATA
Additional help
Declaring Field Symbols
Reward points if useful
Regards
Anji -
Can any one explain me about Field symbols in Genral Reports?
Can any one explain me about Field symbols in Genral Reports?
If possible, plz explain me with the code to explain me about the field symbols.
Regards,
Krishna ChaitanyaSyntax
FIELD-SYMBOLS <fs> { typing | STRUCTURE struc DEFAULT dobj }.
Extras:
1. ... typing
2. ... STRUCTURE struc DEFAULT dobj
Effect
The FIELD-SYMBOLS statement declares a field symbol <fs>. The naming conventions apply to the name fs. The angle brackets of the field symbols indicate the difference to data objects and are obligatory. You can declare field symbols in any procedure and in the global declaration section of an ABAP program, but not in the declaration section of a class or an interface. You can use a field symbol in any operand position in which it is visible and which match the typing defined using typing.
After its declaration, a field symbol is initial - that is, it does not reference a memory area. You have to assign a memory area to it (normally using the ASSIGN statement) before you can use it as an operand. Otherwise an exception will be triggered.
Addition 1
... typing
Effect
You can use the addition typing to type the field symbol. The syntax of typing is described under Syntax of Typing. The typing specifies which memory areas can be assigned to the field symbol (see Checking the Typing) and in which operand positions it can be used.
Note
You can omit the addition typing outside of methods. In this case, the field symbol has the complete generic type any and is implicitly assigned the predefined constant space during the declaration.
Addition 2
... STRUCTURE struc DEFAULT dobj
Effect
If you specify the addition STRUCTURE instead of typing for a field symbol, and struc is a local program structure (a data object, not a data type) or a flat structure from the ABAP Dictionary, this structure is cast for the field symbol <fs>. You have to specify a data object dobj that is initially assigned to the field symbol.
The field symbol copies the technical attributes of structure struc as if it were completely typed. When you assign a data object using the addition DEFAULT, or later using ASSIGN, its complete data type is not checked in non- Unicode programs. Instead, the system merely checks whether it has at least the length of the structure and its alignment.
In Unicode programs, we differentiate between structured and elementary data objects. For a structured data object dobj, its Unicode fragment view has to match the one of struc. In the case of an elementary data object, the object must be character-type and flat, and struc must be purely character-type. The same applies to assignments of data objects to field symbols typed using STRUCTURE when using the ASSIGN statement.
Note
Field symbols declared using the addition STRUCTURE are a mixture of typed field symbols and a utility for casting structured data types. You should use the additions TYPE or LIKE for the FIELD-SYMBOLS statement to type field symbols, while the addition CASTING of the ASSIGN statement is used for casting.
Example
The first example shows the obsolete usage of the addition STRUCTURE.
DATA wa1 TYPE c LENGTH 512.
FIELD-SYMBOLS <scarr1> STRUCTURE scarr DEFAULT wa1.
<scarr1>-carrid = '...'.
The second example shows the replacement of STRUCTURE with the additions TYPE and CASTING.
DATA wa2 TYPE c LENGTH 512.
FIELD-SYMBOLS <scarr2> TYPE scarr.
ASSIGN wa2 TO <scarr2> CASTING.
<scarr2>-carrid = '...'.
Also,
Field Symbols
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects.
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve performance in some cases.
check the below links u will get the answers for your questions
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
http://www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/field_sy.htm
http://searchsap.techtarget.com/tip/1,289483,sid21_gci920484,00.html
Syntax Diagram
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Extras:
1. ... TYPE type
2. ... TYPE REF TO cif
3. ... TYPE REF TO DATA
4. ... TYPE LINE OF type
5. ... LIKE s
6. ... LIKE LINE OF s
7. ... TYPE tabkind
8. ... STRUCTURE s DEFAULT wa
The syntax check performed in an ABAP Objects context is stricter than in other ABAP areas. See Cannot Use Untyped Field Symbols ad Cannot Use Field Symbols as Components of Classes.
Effect
This statement declares a symbolic field called <fs>. At runtime, you can assign a concrete field to the field symbol using ASSIGN. All operations performed with the field symbol then directly affect the field assigned to it.
You can only use one of the additions.
Example
Output aircraft type from the table SFLIGHT using a field symbol:
FIELD-SYMBOLS <PT> TYPE ANY.
DATA SFLIGHT_WA TYPE SFLIGHT.
ASSIGN SFLIGHT_WA-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... TYPE type
Addition 2
... TYPE REF TO cif
Addition 3
... TYPE REF TO DATA
Addition 4
... TYPE LINE OF type
Addition 5
... LIKE s
Addition 6
... LIKE LINE OF s
Addition 7
... TYPE tabkind
Effect
You can define the type of the field symbol using additions 2 to 7 (just as you can for FORM parameters (compare Defining the Type of Subroutine Parameters). When you use the ASSIGN statement, the system carries out the same type checks as for USING parameters of FORMs.
This addition is not allowed in an ABAP Objects context. See Cannot Use Obsolete Casting for FIELD SYMBOLS.
In some cases, the syntax rules that apply to Unicode programs are different than those for non-Unicode programs. See Defining Types Using STRUCTURE.
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP Dictionary (s). All fields of the structure can be addressed by name: <fs>-fieldname. The structured field symbol points initially to the work area wa specified after DEFAULT.
The work area wa must be at least as long as the structure s. If s contains fields of the type I or F, wa should have the structure s or at least begin in that way, since otherwise alignment problems may occur.
Example
Address components of the flight bookings table SBOOK using a field symbol:
DATA SBOOK_WA LIKE SBOOK.
FIELD-SYMBOLS <SB> STRUCTURE SBOOK
DEFAULT SBOOK_WA.
WRITE: <SB>-BOOKID, <SB>-FLDATE.
Related
ASSIGN, DATA
Additional help
Declaring Field Symbols -
Checking whether field-symbol from another program is assigned?
Hi all
I'm attempting to access a FS from another program.
As the FS can be assigned, or unassigned within that program, how do I checked for that in my calling program?
e.g. calling program;
FIELD-SYMBOLS: <fs> TYPE STANDARD TABLE.
DATA: lv_var(40) type c.
lv_var = '(ZTGT_PROG)<read_fs>'.
ASSIGN (lv_var) TO <fs>. " statement might dump...Hi
Go through this doc and use accordingly
Field Symbols
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects.
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve performance in some cases.
check the below links u will get the answers for your questions
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
http://www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/field_sy.htm
http://searchsap.techtarget.com/tip/1,289483,sid21_gci920484,00.html
Syntax Diagram
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Extras:
1. ... TYPE type
2. ... TYPE REF TO cif
3. ... TYPE REF TO DATA
4. ... TYPE LINE OF type
5. ... LIKE s
6. ... LIKE LINE OF s
7. ... TYPE tabkind
8. ... STRUCTURE s DEFAULT wa
The syntax check performed in an ABAP Objects context is stricter than in other ABAP areas. See Cannot Use Untyped Field Symbols ad Cannot Use Field Symbols as Components of Classes.
Effect
This statement declares a symbolic field called <fs>. At runtime, you can assign a concrete field to the field symbol using ASSIGN. All operations performed with the field symbol then directly affect the field assigned to it.
You can only use one of the additions.
Example
Output aircraft type from the table SFLIGHT using a field symbol:
FIELD-SYMBOLS <PT> TYPE ANY.
DATA SFLIGHT_WA TYPE SFLIGHT.
ASSIGN SFLIGHT_WA-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... TYPE type
Addition 2
... TYPE REF TO cif
Addition 3
... TYPE REF TO DATA
Addition 4
... TYPE LINE OF type
Addition 5
... LIKE s
Addition 6
... LIKE LINE OF s
Addition 7
... TYPE tabkind
Effect
You can define the type of the field symbol using additions 2 to 7 (just as you can for FORM parameters (compare Defining the Type of Subroutine Parameters). When you use the ASSIGN statement, the system carries out the same type checks as for USING parameters of FORMs.
This addition is not allowed in an ABAP Objects context. See Cannot Use Obsolete Casting for FIELD SYMBOLS.
In some cases, the syntax rules that apply to Unicode programs are different than those for non-Unicode programs. See Defining Types Using STRUCTURE.
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP Dictionary (s). All fields of the structure can be addressed by name: <fs>-fieldname. The structured field symbol points initially to the work area wa specified after DEFAULT.
The work area wa must be at least as long as the structure s. If s contains fields of the type I or F, wa should have the structure s or at least begin in that way, since otherwise alignment problems may occur.
Example
Address components of the flight bookings table SBOOK using a field symbol:
DATA SBOOK_WA LIKE SBOOK.
FIELD-SYMBOLS <SB> STRUCTURE SBOOK
DEFAULT SBOOK_WA.
WRITE: <SB>-BOOKID, <SB>-FLDATE.
Related
ASSIGN, DATA
Additional help
Declaring Field Symbols
Reward points if useful
Regards
Anji -
HOW CAN I SEND FIELD SYMBOL TO SUBROUTINE
HAI,
HOW CAN I SEND FIELD SYMBOL TO SUBROUTINE
HOW CAN I COME BACK FROM 5TH INTERACTIVE REROT TO 2ND
INTERACTIVE REPORT.
THANK YOU.
ASHOKHi
Write some code in the program to come to 2nd list from 5th list
if sy-lsind = 5.
sy-lsind = 2.
endif.
for field symbols see the doc
Field Symbols
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects.
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve performance in some cases.
check the below links u will get the answers for your questions
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
http://www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/field_sy.htm
http://searchsap.techtarget.com/tip/1,289483,sid21_gci920484,00.html
Syntax Diagram
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Extras:
1. ... TYPE type
2. ... TYPE REF TO cif
3. ... TYPE REF TO DATA
4. ... TYPE LINE OF type
5. ... LIKE s
6. ... LIKE LINE OF s
7. ... TYPE tabkind
8. ... STRUCTURE s DEFAULT wa
The syntax check performed in an ABAP Objects context is stricter than in other ABAP areas. See Cannot Use Untyped Field Symbols ad Cannot Use Field Symbols as Components of Classes.
Effect
This statement declares a symbolic field called <fs>. At runtime, you can assign a concrete field to the field symbol using ASSIGN. All operations performed with the field symbol then directly affect the field assigned to it.
You can only use one of the additions.
Example
Output aircraft type from the table SFLIGHT using a field symbol:
FIELD-SYMBOLS <PT> TYPE ANY.
DATA SFLIGHT_WA TYPE SFLIGHT.
ASSIGN SFLIGHT_WA-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... TYPE type
Addition 2
... TYPE REF TO cif
Addition 3
... TYPE REF TO DATA
Addition 4
... TYPE LINE OF type
Addition 5
... LIKE s
Addition 6
... LIKE LINE OF s
Addition 7
... TYPE tabkind
Effect
You can define the type of the field symbol using additions 2 to 7 (just as you can for FORM parameters (compare Defining the Type of Subroutine Parameters). When you use the ASSIGN statement, the system carries out the same type checks as for USING parameters of FORMs.
This addition is not allowed in an ABAP Objects context. See Cannot Use Obsolete Casting for FIELD SYMBOLS.
In some cases, the syntax rules that apply to Unicode programs are different than those for non-Unicode programs. See Defining Types Using STRUCTURE.
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP Dictionary (s). All fields of the structure can be addressed by name: <fs>-fieldname. The structured field symbol points initially to the work area wa specified after DEFAULT.
The work area wa must be at least as long as the structure s. If s contains fields of the type I or F, wa should have the structure s or at least begin in that way, since otherwise alignment problems may occur.
Example
Address components of the flight bookings table SBOOK using a field symbol:
DATA SBOOK_WA LIKE SBOOK.
FIELD-SYMBOLS <SB> STRUCTURE SBOOK
DEFAULT SBOOK_WA.
WRITE: <SB>-BOOKID, <SB>-FLDATE.
Related
ASSIGN, DATA
Additional help
Declaring Field Symbols
Reward points if useful
Regards
Anji -
Hi all,
Can anyone explains what is Fiels symbol and significance of that with examples?
Thanks
ShivaHI Shiva
Field symbols are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Field symbols are similar to dereferenced pointers in C (that is, pointers to which the content operator * is applied). However, the only real equivalent of pointers in ABAP, that is, variables that contain a memory address (reference) and that can be used without the contents operator, are reference variables in ABAP Objects. (For more information, see Data References).
All operations programmed with field symbols are applied to the field assigned to it. For example, a MOVE statement between two field symbols moves the contents of the field assigned to the first field symbol to the field assigned to the second field symbol. The field symbols themselves point to the same fields after the MOVE statement as they did before.
You can create field symbols either without or with type specifications. If you do not specify a type, the field symbol inherits all of the technical attributes of the field assigned to it. If you do specify a type, the system checks the compatibility of the field symbol and the field you are assigning to it during the ASSIGN statement.
Field symbols provide greater flexibility when you address data objects:
If you want to process sections of fields, you can specify the offset and length of the field dynamically.
You can assign one field symbol to another, which allows you to address parts of fields.
Assignments to field symbols may extend beyond field boundaries. This allows you to address regular sequences of fields in memory efficiently.
You can also force a field symbol to take different technical attributes from those of the field assigned to it.
The flexibility of field symbols provides elegant solutions to certain problems. On the other hand, it does mean that errors can easily occur. Since fields are not assigned to field symbols until runtime, the effectiveness of syntax and security checks is very limited for operations involving field symbols. This can lead to runtime errors or incorrect data assignments.
While runtime errors indicate an obvious problem, incorrect data assignments are dangerous because they can be very difficult to detect. For this reason, you should only use field symbols if you cannot achieve the same result using other ABAP statements.
For example, you may want to process part of a string where the offset and length depend on the contents of the field. You could use field symbols in this case. However, since the MOVE statement also supports variable offset and length specifications, you should use it instead. The MOVE statement (with your own auxiliary variables if required) is much safer than using field symbols, since it cannot address memory beyond the boundary of a field. However, field symbols may improve
To declare a field symbol, use the statement
FIELD-SYMBOLS <FS> [<type>|STRUCTURE <s> DEFAULT <wa>].
For field symbols, the angle brackets are part of the syntax. They identify field symbols in the program code.
If you do not specify any additions, the field symbol <FS> can have data objects of any type assigned to it. When you assign a data object, the field symbol inherits its technical attributes. The data type of the assigned data object becomes the actual data type of the field symbol.
Note: it is possible to assign reference variables and structured data objects to untyped field symbols. However, the static field symbol is only a pointer to the field in memory, and does not have the complex type attributes of a reference or structured field until runtime. You can only use the field symbol to address the whole field (for example, in a MOVE statement). Specific statements such as CREATE OBJECT <FS> or LOOP AT <FS> are not possible.
Typing Field Symbols
The <type> addition allows you to specify the type of a field symbol. When you assign a data object to a field symbol, the system checks whether the type of the data object you are trying to assign is compatible with that of the field symbol. If the types are not compatible or convertible, the system reacts with a syntax or runtime error. If however, you want to assign the type of the field symbol to the data object by means of casting, you must do so explicitly using the ASSIGN statement. The system then treats the assigned data object as if it had the same type as the field symbol.
You specify the type of a field symbol using the same semantics as for formal parameters in procedures. For <type> you can enter either TYPE <t> or LIKE <f>. You can specify the type either generically or in full. If you specify a generic type, the type of the field symbol is either partially specified or not specified at all. Any attributes that are not specified are inherited from the corresponding data object in the ASSIGN statement. If you specify the type fully, all of the technical attributes of the field symbol are determined when you define it. You can then only assign data objects to it that have exactly the same data type.
You should always specify a type for each field symbol. If you cannot avoid defining a generic field symbol, make this clear by using an appropriate generic type declaration.
Generic Type Specification
The following types allow you more freedom when using actual parameters. The data object only needs to have the selection of attributes specified.
Typing
Check for data object
No type specification
TYPE ANY
All types of data object are accepted. The field symbol adopts all of the attributes of the data object.
TYPE C, N, P, or X
Only data objects with type C, N, P, or X are accepted. The field symbol adopts the field length and DECIMALS specification (type P) of the data object.
TYPE TABLE
The system checks whether the data object is a standard internal table. This is a shortened form of TYPE STANDARD TABLE (see below).
TYPE ANY TABLE
The system checks whether the data object is an internal table. The field symbol inherits all of the attributes (line type, table type, key) from the data object.
TYPE INDEX TABLE
The system checks whether the data object is an index table (standard or sorted table). The field symbol inherits all of the attributes (line type, table type, key) from the data object.
TYPE STANDARD TABLE
The system checks whether the data object is a standard internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
TYPE SORTED TABLE
The system checks whether the actual parameter is a sorted internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
TYPE HASHED TABLE
The system checks whether the actual parameter is a hashed internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
If you specify a type generically, remember that the attributes inherited by the field symbol from the program are not statically recognizable in the program. You can, at most, address them dynamically.
TYPES: BEGIN OF line,
col1 TYPE c,
col2 TYPE c,
END OF line.
DATA: wa TYPE line,
itab TYPE HASHED TABLE OF line WITH UNIQUE KEY col1,
key(4) TYPE c VALUE 'COL1'.
FIELD-SYMBOLS <fs> TYPE ANY TABLE.
ASSIGN itab TO <fs>.
READ TABLE <fs> WITH TABLE KEY (key) = 'X' INTO wa.
The internal table ITAB is assigned to the generic field symbol <FS>, after which it is possible to address the table key of the field symbol dynamically. However, the static address
READ TABLE <fs> WITH TABLE KEY col1 = 'X' INTO wa.
is not possible syntactically, since the field symbol does not adopt the key of table ITAB until runtime. In the program, the type specification ANY TABLE only indicates that <FS> is a table. If the type had been ANY (or no type had been specified at all), even the specific internal table statement READ TABLE <FS> would not have been possible.
If you adopt a structured type generically (a structure, or a table with structured line type), the individual components cannot be addressed in the program either statically or dynamically. In this case, you would have to work with further field symbols and the method of assigning structures component by component.
Specifying the Type Fully
When you use the following types, the technical attributes of the field symbols are fully specified. The technical attributes of the data objects must correspond to those of the field symbol.
Typing
Technical attributes of the field symbol
TYPE D, F, I, or T
The field symbol has the technical attributes of the predefined elementary type
TYPE <type>
The field symbol has the type <type>. This is a data type defined within the program using the TYPES statement, or a type from the ABAP Dictionary
TYPE REF TO <cif>|DATA
The field symbol is a reference variable for the class or interface <cif>, or for a data object.
TYPE LINE OF <itab>
The field symbol has the same type as a line of the internal table <itab> defined using a TYPES statement or defined in the ABAP Dictionary
LIKE <f>
The field symbol has the same type as an internal data object <f> or structure, or a database table from the ABAP Dictionary
When you use a field symbol that is fully typed, you can address its attributes statically in the program, since they are recognized in the source code. If you fully specify the type of a field symbol as a reference or structured data object, you can address it as you would the data object itself, once you have assigned an object to it. So, for example, you could address the components of a structure, loop through an internal table, or create an object with reference to a field symbol.
REPORT demo_field_symbols_type .
DATA: BEGIN OF line,
col1(1) TYPE c,
col2(1) TYPE c VALUE 'X',
END OF line.
FIELD-SYMBOLS <fs> LIKE line.
ASSIGN line TO <fs>.
MOVE <fs>-col2 TO <fs>-col1.
The field symbol <FS> is fully typed as a structure, and you can address its components in the program.
Attaching a structure to a field symbol
The STRUCTURE addition forces a structured view of the data objects that you assign to a field symbol.
FIELD-SYMBOLS <FS> STRUCTURE <s> DEFAULT <f>.
The structure <s> is either a structured local data object in the program, or a flat structure from the ABAP Dictionary. <f> is a data object that must be assigned to the field symbol as a starting field. However, this assignment can be changed later using the ASSIGN statement.
When you assign a data object to the field symbol, the system only checks that it is at least as long as the structure. You can address the individual components of the field symbol. It has the same technical attributes as the structure <s>.
If <s> contains components with type I or F, you should remember the possible effects of alignment. When you assign a data object to a field symbol with a structure, the data object must have the same alignment, otherwise a runtime error may result. In such cases, you are advised to assign such data objects only to structured field symbols, which retain the same structure as the field symbol at least over the length of the structure.
The STRUCTURE is obsolete; you should no longer use it. Field symbols defined using the STRUCTURE addition are a mixture of typed field symbols and a utility for casting to either local or ABAP Dictionary data types. If you want to define the type of a field symbol, include the TYPE addition in a FIELD-SYMBOLS statement. If you want to use casting, include the CASTING addition in an ASSIGN statement.
Example using the obsolete STRUCTURE addition:
DATA: wa(10) VALUE '0123456789'.
DATA: BEGIN OF line1,
col1(3),
col2(2),
col3(5),
END OF line1.
DATA: BEGIN OF line2,
col1(2),
col2 LIKE sy-datum,
END OF line2.
FIELD-SYMBOLS: <f1> STRUCTURE line1 DEFAULT wa,
<f2> STRUCTURE line2 DEFAULT wa.
WRITE: / <f1>-col1, <f1>-col2, <f1>-col3,
/ <f2>-col1, <f2>-col2.
Example using the correct syntax (TYPE and CASTING):
DATA: wa(10) VALUE '0123456789'.
DATA: BEGIN OF line1,
col1(3),
col2(2),
col3(5),
END OF line1.
DATA: BEGIN OF line2,
COL1(2),
COL2 LIKE sy-datum,
END OF line2.
FIELD-SYMBOLS: <f1> LIKE line1.
ASSIGN wa TO <f1> CASTING.
FIELD-SYMBOLS: <f2> LIKE line2.
ASSIGN wa TO <f2> CASTING.
WRITE: / <f1>-col1, <F1>-col2, <F1>-col3,
/ <f2>-col1, <F2>-col2.
In both cases, the list appears as follows:
012 34 56789
01 2345/67/89
This example declares two field symbols to which different structures are attached. The string WA is then assigned to each of them. The output shows that the field symbols assign the strings component by component according to the type of the components.
Assigning Components of Structures to a Field Symbol
For a structured data object <s>, you can use the statement
ASSIGN COMPONENT <comp> OF STRUCTURE <s> TO <FS>.
to assign one of its components <comp> to the field symbol <FS>. You can specify the component <comp> either as a literal or a variable. If <comp> is of type C or a structure that has no internal tables as components, it specifies the name of the component. If <comp> has any other elementary data type, it is converted to type I and specifies the number of the component. If the assignment is successful, SY-SUBRC is set to 0. Otherwise, it is set to 4.
This statement is particularly important for addressing components of structured data objects dynamically. If you assign a data object to a field symbol either generically or using casting, or pass it generically (or using casting) to the parameter interface of a procedure, you cannot address its components either statically or dynamically. Instead, you must use the above statement. This allows indirect access either using the component name or its index number.
DATA: BEGIN OF LINE,
COL1 TYPE I VALUE '11',
COL2 TYPE I VALUE '22',
COL3 TYPE I VALUE '33',
END OF LINE.
DATA COMP(5) VALUE 'COL3'.
FIELD-SYMBOLS: <F1>, <F2>, <F3>.
ASSIGN LINE TO <F1>.
ASSIGN COMP TO <F2>.
DO 3 TIMES.
ASSIGN COMPONENT SY-INDEX OF STRUCTURE <F1> TO <F3>.
WRITE <F3>.
ENDDO.
ASSIGN COMPONENT <F2> OF STRUCTURE <F1> TO <F3>.
WRITE / <F3>.
The output is:
11 22 33
33
The field symbol <F1> points to the structure LINE, <F2> points to the field COMP. In the DO loop, the components of LINE are specified by their numbers and assigned one by one to <F3>. After the loop, the component COL3 of LINE is specified by its name and assigned to <F3>. Note that ASSIGN COMPONENT is the only possible method of addressing the components of <F1>. Expressions such as <F1>-COL1 are syntactically incorrect.
Regards,
Laxmi. -
Hello :i would like to ask one favor , how can i define a field symbol, that can recieve a dynamic variable
segment of code:
CALL METHOD cl_alv_table_create=>create_dynamic_table
EXPORTING
it_fieldcatalog = it_fldcat
IMPORTING
ep_table = it_dynamic.
ASSIGN it_dynamic->* TO <dyn_table>.
CREATE DATA wa_dynamic LIKE line of <dyn_table>.
ASSIGN wa_dynamic->* TO <dyn_wa>. " this one 'wa_dynamic' i need to sent to <dyn_wa>
thanks a lotHI
GOOD
Generic Type Specification
The following types allow you more freedom when using actual parameters. The data object only needs to have the selection of attributes specified.
Typing
Check for data object
No type specification
TYPE ANY
All types of data object are accepted. The field symbol adopts all of the attributes of the data object.
TYPE C, N, P, or X
Only data objects with type C, N, P, or X are accepted. The field symbol adopts the field length and DECIMALS specification (type P) of the data object.
TYPE TABLE
The system checks whether the data object is a standard internal table. This is a shortened form of TYPE STANDARD TABLE (see below).
TYPE ANY TABLE
The system checks whether the data object is an internal table. The field symbol inherits all of the attributes (line type, table type, key) from the data object.
TYPE INDEX TABLE
The system checks whether the data object is an index table (standard or sorted table). The field symbol inherits all of the attributes (line type, table type, key) from the data object.
TYPE STANDARD TABLE
The system checks whether the data object is a standard internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
TYPE SORTED TABLE
The system checks whether the actual parameter is a sorted internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
TYPE HASHED TABLE
The system checks whether the actual parameter is a hashed internal table. The field symbol inherits all of the remaining attributes (line type, key) from the data object.
If you specify a type generically, remember that the attributes inherited by the field symbol from the program are not statically recognizable in the program. You can, at most, address them dynamically.
TYPES: BEGIN OF line,
col1 TYPE c,
col2 TYPE c,
END OF line.
DATA: wa TYPE line,
itab TYPE HASHED TABLE OF line WITH UNIQUE KEY col1,
key(4) TYPE c VALUE 'COL1'.
FIELD-SYMBOLS <fs> TYPE ANY TABLE.
ASSIGN itab TO <fs>.
READ TABLE <fs> WITH TABLE KEY (key) = 'X' INTO wa.
The internal table ITAB is assigned to the generic field symbol <FS>, after which it is possible to address the table key of the field symbol dynamically. However, the static address
READ TABLE <fs> WITH TABLE KEY col1 = 'X' INTO wa.
is not possible syntactically, since the field symbol does not adopt the key of table ITAB until runtime. In the program, the type specification ANY TABLE only indicates that <FS> is a table. If the type had been ANY (or no type had been specified at all), even the specific internal table statement READ TABLE <FS> would not have been possible.
If you adopt a structured type generically (a structure, or a table with structured line type), the individual components cannot be addressed in the program either statically or dynamically. In this case, you would have to work with further field symbols and the method of assigning structures component by component.
Specifying the Type Fully
When you use the following types, the technical attributes of the field symbols are fully specified. The technical attributes of the data objects must correspond to those of the field symbol.
Typing
Technical attributes of the field symbol
TYPE D, F, I, or T
The field symbol has the technical attributes of the predefined elementary type
TYPE <type>
The field symbol has the type <type>. This is a data type defined within the program using the TYPES statement, or a type from the ABAP Dictionary
TYPE REF TO <cif>|DATA
The field symbol is a reference variable for the class or interface <cif>, or for a data object.
TYPE LINE OF <itab>
The field symbol has the same type as a line of the internal table <itab> defined using a TYPES statement or defined in the ABAP Dictionary
LIKE <f>
The field symbol has the same type as an internal data object <f> or structure, or a database table from the ABAP Dictionary
When you use a field symbol that is fully typed, you can address its attributes statically in the program, since they are recognized in the source code. If you fully specify the type of a field symbol as a reference or structured data object, you can address it as you would the data object itself, once you have assigned an object to it. So, for example, you could address the components of a structure, loop through an internal table, or create an object with reference to a field symbol.
REPORT demo_field_symbols_type .
DATA: BEGIN OF line,
col1(1) TYPE c,
col2(1) TYPE c VALUE 'X',
END OF line.
FIELD-SYMBOLS <fs> LIKE line.
ASSIGN line TO <fs>.
MOVE <fs>-col2 TO <fs>-col1.
The field symbol <FS> is fully typed as a structure, and you can address its components in the program.
Attaching a structure to a field symbol
The STRUCTURE addition forces a structured view of the data objects that you assign to a field symbol.
FIELD-SYMBOLS <FS> STRUCTURE <s> DEFAULT <f>.
The structure <s> is either a structured local data object in the program, or a flat structure from the ABAP Dictionary. <f> is a data object that must be assigned to the field symbol as a starting field. However, this assignment can be changed later using the ASSIGN statement.
When you assign a data object to the field symbol, the system only checks that it is at least as long as the structure. You can address the individual components of the field symbol. It has the same technical attributes as the structure <s>.
If <s> contains components with type I or F, you should remember the possible effects of alignment. When you assign a data object to a field symbol with a structure, the data object must have the same alignment, otherwise a runtime error may result. In such cases, you are advised to assign such data objects only to structured field symbols, which retain the same structure as the field symbol at least over the length of the structure.
The STRUCTURE is obsolete; you should no longer use it. Field symbols defined using the STRUCTURE addition are a mixture of typed field symbols and a utility for casting to either local or ABAP Dictionary data types. If you want to define the type of a field symbol, include the TYPE addition in a FIELD-SYMBOLS statement. If you want to use casting, include the CASTING addition in an ASSIGN statement.
Example using the obsolete STRUCTURE addition:
DATA: wa(10) VALUE '0123456789'.
DATA: BEGIN OF line1,
col1(3),
col2(2),
col3(5),
END OF line1.
DATA: BEGIN OF line2,
col1(2),
col2 LIKE sy-datum,
END OF line2.
FIELD-SYMBOLS: <f1> STRUCTURE line1 DEFAULT wa,
<f2> STRUCTURE line2 DEFAULT wa.
WRITE: / <f1>-col1, <f1>-col2, <f1>-col3,
/ <f2>-col1, <f2>-col2.
Example using the correct syntax (TYPE and CASTING):
DATA: wa(10) VALUE '0123456789'.
DATA: BEGIN OF line1,
col1(3),
col2(2),
col3(5),
END OF line1.
DATA: BEGIN OF line2,
COL1(2),
COL2 LIKE sy-datum,
END OF line2.
FIELD-SYMBOLS: <f1> LIKE line1.
ASSIGN wa TO <f1> CASTING.
FIELD-SYMBOLS: <f2> LIKE line2.
ASSIGN wa TO <f2> CASTING.
WRITE: / <f1>-col1, <F1>-col2, <F1>-col3,
/ <f2>-col1, <F2>-col2.
In both cases, the list appears as follows:
012 34 56789
01 2345/67/89
This example declares two field symbols to which different structures are attached. The string WA is then assigned to each of them. The output shows that the field symbols assign the strings component by component according to the type of the components.
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb387a358411d1829f0000e829fbfe/content.htm
THANKS
MRUTYUN
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