SAP ABAP, Variable Variables

I was modifying an ABAP program for a migration project and came across a section of code that was initially puzzling to me. I couldn't figure out why the previous developer was filling variables with field names and then assigning those variables to field symbols, until I noticed the parentheses surrounding the variable name in the assign statement. The previous developer create a variable to hold the name of a field (another variable), he then used the ASSIGN keyword to assign the parenthesized variable it to a field symbol. Field symbols are a type of memory pointer, so the field symbol pointed to the memory location specified by the value of the variable.

This sounds quite a bit more confusing than it really is, so I wrote a small sample program to demonstrate the technique. This is not something that should normally be required, but in the case I was dealing with we were parsing a table row by row and field by field in order to transform the data for migration into a different SAP system.



DATA: lv_variable(30) TYPE c,
lv_variable_name(30) TYPE c.
FIELD-SYMBOLS: <fs_test1>,

" This is the actual variable we are working with
"MOVE 'this is a test string' TO lv_variable.

lv_variable = 'this is a test string'.

" This is the name of the variable we are working with
"MOVE 'lv_variable' TO lv_variable_name.

lv_variable_name = 'lv_variable'.

" Assign the variable name to the field symbol
" (really point the field symbol to the variable)

ASSIGN lv_variable_name TO <fs_test1>.

" Assign the contents of the mentioned
" variable name to the field symbol
" (really point the field symbol to the variable
" name that is defined in the variable)
" The parentheses are used to dereference,
" allowing variable "variable names"

ASSIGN (lv_variable_name) TO <fs_test2>.

WRITE lv_variable.
WRITE lv_variable_name.
WRITE <fs_test1>.
WRITE <fs_test2>.

And here is the output:

this is a test string



this is a test string
Published: 2010-11-19