Field symbols to structures

when a run time error occurs using field symbols of structures to data objects corresponds to alignment.?
please explain with an example.

I think it would be better for you to explain what you are doing and what the runtime error is all about.
Because: 'field symbols of structures to data objects corresponds to alignment' doesn't ring a bell for any of us obviously.

Similar Messages

Dynamic Field Symbols with Structures

Hello,
I am stuck on a piece of code and looking for some help. I am trying to figure out how to assign values in a structure of a dynamically defined field symbol to the structure inside another dynamically defined field symbol. Here is my code and some comments. Basically I am uploading data via a flatfile and placing it into a dynamically defined field symbol.
DATA:
lr_area     TYPE REF TO cl_sem_planarea_attributes,
lr_t_data   TYPE REF TO data,
lr_s_data   TYPE REF TO data,
lr_s_chas   TYPE REF TO data,
lr_s_kyfs   TYPE REF TO data.
FIELD-SYMBOLS:
<lt_data> TYPE STANDARD TABLE,
<ls_data> TYPE ANY,
<ls_chas> TYPE ANY,
<ls_kyfs> TYPE ANY.
DATA: ls_chasel TYPE upc_ys_chasel,
ls_charng TYPE upc_ys_charng.
FIELD-SYMBOLS:
<f> TYPE ANY,
<chas> TYPE TABLE,
<kyfs> TYPE ANY.
CALL METHOD cl_sem_planarea_attributes=>get_instance
EXPORTING       i_area      = i_area
RECEIVING       er_instance = lr_area.
CHECK sy-subrc = 0.
CREATE DATA lr_s_data TYPE (lr_area->typename_s_data).
ASSIGN lr_s_data->*   TO <ls_data>.
CREATE DATA lr_t_data TYPE (lr_area->typename_t_data).
ASSIGN lr_t_data->*   TO <lt_data>.
CREATE DATA lr_s_chas TYPE (lr_area->typename_s_chas).
ASSIGN lr_s_chas->*   TO <ls_chas>.
CREATE DATA lr_s_kyfs TYPE (lr_area->typename_s_kyfs).
ASSIGN lr_s_kyfs->*   TO <ls_kyfs>.
LOOP AT gt_file INTO ls_file.
CLEAR <ls_data>.
MOVE-CORRESPONDING ls_file TO <ls_kyfs>. " Map key figures
MOVE-CORRESPONDING ls_file TO <ls_chas>. " Map chars
*    MOVE-CORRESPONDING ls_file TO <ls_data>. " Map data
*        ASSIGN COMPONENT 'ls_chas' OF STRUCTURE <ls_Data> TO <chas> .
*        IF sy-subrc = 0.
**          <chas> = <ls_chas>.
*MOVE-CORRESPONDING <ls_chas> to <chas>.
*        ENDIF.
<chas> = <ls_chas>.
LOOP AT <chas> INTO ls_chasel.
READ TABLE ls_chasel-t_charng INTO ls_charng INDEX 1.
IF sy-subrc = 0 AND ls_charng-option = 'EQ'.
ASSIGN COMPONENT ls_chasel-chanm OF STRUCTURE <ls_chas> TO <ls_data>.
IF sy-subrc = 0.
<ls_data> = ls_charng-low.
ENDIF.
ENDIF.
ENDLOOP.
COLLECT <ls_data> INTO <lt_data>.
ENDLOOP.
Ls_chasel has 2 components:
Chanm (a char 30 which contains the component’s name)
T_CHARNG (a table with values for chanm)
Ls_data has 2 components:
S_chas (a structure with a list of components and values – same list as would have)
S_kyfs (a structure with a list of components and values – same list as would have)
Lt_data is a table of ls_data
I need to get the data in ls_chas into the ls_chas structure of ls_data and the ls_kyfs data into the ls_kyfs structure of ls_chas and append ls_chas to lt_data. Anything that is commented out is something I tried that didn't work. RIght now I get a dump at the 'loop at <chas> into ls_chasel' that the field symbol is not assigned.
Thanks for your help!

It looks like the the original poster didn't completely understand all he was doing. (This is why I always recommend getting an ABAP programmer in for what is, essentially, advanced ABAP programming, rather than someone "kind of familiar" with ABAP trying it - we're often available at very reasonable rates ).
It seems he's using ito_chasel to set the fixed values (which is in fact quite smart!). What isn't required, so far as I can tell without implementing, are any of the statements involving <ls_kyfs> or <ls_chas>.
The following should be sufficient (with the necessary declarations etc. - but really: omit <ls_kyfs> and <ls_chas> - I'm sure they're not needed and they confuse things).
" Go through the data from the flat file
LOOP AT gt_file INTO ls_file.
CLEAR <ls_data>.
" Transfer the characteristics
MOVE-CORRESPONDING ls_file TO <s_chas>.
" Transfer the key figure
MOVE-CORRESPONDING ls_file TO <s_kyfs>.
" Go through the fixed characteristic selections from the package
LOOP AT ito_chasel INTO ls_chasel.
    " We only care about the first value (if there is one).
    READ TABLE ls_chasel-s_charng INTO ls_charng INDEX 1.
    " Check there is a first value and that it is fixed
    CHECK sy-subrc IS INITIAL AND ls_charng EQ 'EQ'.
    " Get access to that characteristic
    FIELD-SYMBOLS <fixed_value> TYPE ANY.
    ASSIGN COMPONENT ls_chasel-chanm OF STRUCTURE <s_chas> TO <fixed_value>.
    " Make sure that it exists in the data structure
    CHECK sy-subrc IS INITIAL.
    " Set the value
    <fixed_value> = ls_charng-low.
ENDLOOP.
COLLECT <ls_data> INTO <lt_data>.
ENDLOOP.

Reading a field symbol whose structure is dynamic

Hi Experts,
I have used the concept of dynamic internal tables to select data from COSS/COSP for e.g.database tables.Field symbol of type " ANY TABLE" has been used to select data , as the dynamic structure is assigned directly to the field symbol.
To calculate the values of various fields I need to read the this field symbol for diferent line items , but I get a compilation error saying " Key not Found ". I understand that I am not able to read the field symbol because its structure is of type 'ANY TABLE' .How do I read this field symbol ?
The field symbol gets the structure of dynamic internal table as formed initially by using class concept.Is their any way in which I could get the structure of this field symbol or any other way to read it?
Thanks in advance.
Regards
Reetwika

Hi Ritwika,
Even if u use the concept if dynamic internal table, u can read the each of the field of ur structure,
if u know the name of the field.
for example:
MATNR being one of the field of internal table
field-symbols : <fs> type any.
loop at <fs_it> into <fs_wa>.
ASSIGN COMPONENT 'MATNR' OF STRUCTURE <fs_wa> to <fs_matnr>.
" in this case matnr field value will be assigned to the field symbol <fs_matnr>, so it can be used further.
endloop.
" do reply if still confused.
Rohit G
Edited by: Rohit Gaharwar on Aug 12, 2009 11:51 AM

Mapping individual field symbols to a structure

Hi,
I have a requirement where I need to map some individual field symbols to some specific fields in a structure:.
Here is what mt code looks like :
data: <f1>, <f2> , <f3>,
       <f4> type ZCUSTTAB.
data: upd type ZCUSTTAB.
data : fieldname1(30),
      fieldname2(20),
      fieldname3(20),
      fname1(20),
      fname2(20),
      fname3(20).
fname1 = 'TOUR_ID'.
fname2 = 'VISIT_ID'.
fname3 = 'CUSTNR'.
concatenate 'ZCUSTTAB-' fname1 into fieldname1.
concatenate 'ZCUSTTAB-' fname2 into fieldname2.
concatenate 'ZCUSTTAB-' fname3 into fieldname3.
assign fieldname1 to <f1>.
assign fieldname2 to <f2>.
assign fieldname3 to <f3>.
<f1> = '12345'.
<f2> = '1'.
<f2> = '123'.
So, at this point I have my field symbols pointing towards individual fields , i.e.
<f1> holds value for ZCUSTTAB-TOUR_ID.
<f2> holds value for ZCUSTTAB-VISIT_ID.
<f3> holds value for ZCUSTTAB-CUSTNR.
Now, I want to move these individual values to a structure which is of type ZCUSTTAB, using which I can update the table ZCUSTTAB at DB.
Any ideas on how to achieve this ?
Thanks-

Hi
U need to declar that table and that's all:
TABLES ZCUSTTAB.
data: <f1>, <f2> , <f3>,
       <f4> type ZCUSTTAB.
data: upd type ZCUSTTAB.
data : fieldname1(30),
      fieldname2(20),
      fieldname3(20),
      fname1(20),
      fname2(20),
      fname3(20).
fname1 = 'TOUR_ID'.
fname2 = 'VISIT_ID'.
fname3 = 'CUSTNR'.
concatenate 'ZCUSTTAB-' fname1 into fieldname1.
concatenate 'ZCUSTTAB-' fname2 into fieldname2.
concatenate 'ZCUSTTAB-' fname3 into fieldname3.
assign fieldname1 to <f1>.
assign fieldname2 to <f2>.
assign fieldname3 to <f3>.
<f1> = '12345'.
<f2> = '1'.
<f2> = '123'.
UPDATE ZCUSTTAB.
After assigning the field-symbols the structure ZCUSTTAB will be filled automatically.
U can also write:
TABLES ZCUSTTAB.
data: <f1>, <f2> , <f3>,
       <f4> type ZCUSTTAB.
data: upd type ZCUSTTAB.
data : fieldname1(30),
      fieldname2(20),
      fieldname3(20),
      fname1(20),
      fname2(20),
      fname3(20).
fname1 = 'TOUR_ID'.
fname2 = 'VISIT_ID'.
fname3 = 'CUSTNR'.
assign component fname1 of structure ZCUSTTAB to <f1>.
assign component fname2 of structure ZCUSTTAB to <f2>.
assign component fname3 of structure ZCUSTTAB to <f3>.
<f1> = '12345'.
<f2> = '1'.
<f2> = '123'.
UPDATE ZCUSTTAB.
Max

How to populate one internal table from another using field symbols

Hi Gurus,
I have a problem. I have to populate one internal table (sructure t_otput) from another internal table (sructure t_from) using field symbol.
Structure for from table.
types: begin of t_from,
         year(4) type c,
         ww(2) type c,
         site type marc-werks,
         demand type i,
       end of t_from.
Structure for output table.
types: begin of t_display,
         title(30),
         WW1(10),
         WW2(10),
         WW3(10),
       end of t_display.
The from table looks like this:
Year | WW | Site | Demand
2005 | 1 | OR1 | 12.00
2005 | 2 | OR1 | 13.00
2005 | 3 | OR1 | 14.00
The display table which has to be populated should look like this:
Title | WW1   | WW2   | WW3
OR1    |       |       |
Demand | 12.00 | 13.00 | 14.00
How to populate display table using field symbol?
Please give code snippets
Thanks,
Gopal

Gopal,
Here is the code, however I am not vary clear about the ORG1 and Demand display that you have shown in the display. I am sure with this code it should not be a big deal to tweak in whatever manner you want.
TABLES : marc.
TYPES: BEGIN OF type_display,
title(30),
ww1(10),
ww2(10),
ww3(10),
END OF type_display.
TYPES: BEGIN OF type_from,
year(4) TYPE c,
ww(2) TYPE c,
site TYPE marc-werks,
demand TYPE i,
END OF type_from.
data : t_from type table of type_from,
       t_display type table of type_display.
field-symbols : <fs_from> type type_from,
                <fs_display> type type_display.
data : wa_from type type_From,
       wa_display type type_display.
wa_from-year = '2005'.
wa_from-ww   = '1'.
wa_from-site = 'OR1'.
wa_from-demand = '12.00'.
insert wa_from into table t_from.
wa_from-year = '2005'.
wa_from-ww   = '2'.
wa_from-site = 'OR1'.
wa_from-demand = '13.00'.
insert wa_from into table t_from.
wa_from-year = '2005'.
wa_from-ww   = '3'.
wa_from-site = 'OR1'.
wa_from-demand = '14.00'.
insert wa_from into table t_from.
data : variable(3) type c.
field-symbols : <fs_any> type any.
break-point.
Loop at t_from assigning <fs_from>.
variable = 'WW'.
wa_display-title = <fs_from>-site.
concatenate variable <fs_from>-ww into variable.
assign component variable of structure wa_display to <fs_any>.
<fs_any> = <fs_from>-demand.
endloop.
append wa_display to t_display.
clear wa_display.
loop at t_display assigning <Fs_display>.
write :/ <fs_display>.
endloop.
Note : Please award points if this helps you.
Regards,
Ravi

How to use field symbols

can anyone tell me how to use field symbols. What effect it has on performance of a program?
what r its avantages?
iam working on a report where iam facing a lot of problems in performance issue. can anyone tell how field symbols are useful in this regard?
thanx to all

Check the below links
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Additions
1. ... STRUCTURE s DEFAULT wa
2. ... TYPE t
3. ... TYPE LINE OF t
4. ... LIKE s
5. ... LIKE LINE OF s
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>.
TABLES SFLIGHT.
ASSIGN SFLIGHT-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... STRUCTURE s DEFAULT wa
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP/4 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.
Addition 2
... TYPE t
Addition 3
... TYPE LINE OF t
Addition 4
... LIKE s
Addition 5
... LIKE LINE OF s
Effect
You can use additions 2 to 5 to type field symbols in the same way as FORM parameters (see also Type assignment of subroutine parameters). ASSIGN performs the same type checks as with USING parameters of FORM s.

How to use field symbol in select

Hi,
    CONCATENATE 'WTG0' LV_MON INTO LV_FNAME.
    ASSIGN (LV_FNAME) TO <FS>.
    SELECT SINGLE <FS> FROM COSP INTO LV_SAPRST
         WHERE OBJNR = LV_OBJ AND GJAHR = LV_YEAR AND WRTTP = '4' AND KSTAR = GT_INOUT-SAKNR
   Error message :    Unknown column name "<FS>" . field list. . field list. field list.
   actually , if i use if command, i can do, but i want to use simple code by fieldsymbol.
   is it possible in select command?
Thanks in advance
Benjamin

Hi
Hope it will help you.
reward if help.
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

How to use field symbols in program

how to use field symbols can any one explain with example please..
Regards,
venki...

Hi
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.
<b>Reward points for useful Answers</b>
Regards
Anji

Field symbols?

Hi,
Can any one give me clear idea of field symbols and their use in the programing?
i read some help docs but could not get it what exactly it means
Thanks,
Ravi

Hi
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.
Regards
Anji

Field Symbols /Field Groups

Hi,
What is the use of Field Symbols and Field Groups?
pls explain me.
My email addr [email protected]

Hi Siva,
Check the below links
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb3860358411d1829f0000e829fbfe/content.htm
FIELD-SYMBOLS
Basic form
FIELD-SYMBOLS <fs>.
Additions
1. ... STRUCTURE s DEFAULT wa
2. ... TYPE t
3. ... TYPE LINE OF t
4. ... LIKE s
5. ... LIKE LINE OF s
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>.
TABLES SFLIGHT.
ASSIGN SFLIGHT-PLANETYPE TO <PT>.
WRITE <PT>.
Addition 1
... STRUCTURE s DEFAULT wa
Effect
Assigns any (internal) field string or structure to the field symbol from the ABAP/4 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.
Addition 2
... TYPE t
Addition 3
... TYPE LINE OF t
Addition 4
... LIKE s
Addition 5
... LIKE LINE OF s
Effect
You can use additions 2 to 5 to type field symbols in the same way as FORM parameters (see also Type assignment of subroutine parameters). ASSIGN performs the same type checks as with USING parameters of FORM s.
<b>Field Groups</b>
http://help.sap.com/saphelp_46c/helpdata/EN/d2/cb43e6455611d189710000e8322d00/content.htm

Field Symbols, Field String, and Field Group.

Hi,
Can you differentiate between filed symbols, field strings and field groups,
With regards,
Bharath Mohan B

Hi,
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.
rgds

Hi
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

What exactly are Field symbols?

Hi SDN,
What exactly are Field symbols?
I have read they are not pointers then what are they?
Regards,
Rahul

Hi
see this
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.
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 Chaitanya

Syntax
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

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

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