Create data

[Former Member]

Why i can do that?

data gf_v1 type n length 5.
data gr_v1 type ref to data.


start-of-selection.
  gf_v1 = 3423.

  create data gr_v1 like gf_v1.
  gr_v1 = 1111.
  break-point.

end-of-selection.

The error message is

The type of GR_V1 cannot converted to the type of "1111".

[Former Member]

You use CREATE DATA usually when you don't know the type of the data you are using until run time.

If you are a beginner, leave it for now, and come back to the issue when you've thoroughly learned the basics.

matt

[Former Member]

Hi,

In order to create data, you need to create a field symbol first and then assign it to field symbol.

Correction in your program:

data gf_v1 type n length 5.
data gr_v1 type ref to data.
 

FIELD-SYMBOLS <fs> TYPE ANY.
 
start-of-selection.
  gf_v1 = 3423.
 
  create data gr_v1 like gf_v1.
   ASSIGN gr_v1->* TO <fs>.

     <fs> = 1111.

  break-point.
 
end-of-selection.

[Former Member]

i haven't understand..

can you write in my code...

[matt]

Marty.

Have you read the ABAP documentation on CREATE DATA.

> CREATE DATA gr_v1 LIKE gf_v1.

creates a reference to some data that has the same structure as gf_v1. I.e. a place in memory. gr_v1 refers (or "points to") this place in memory.

To get to the actual value you have to use field symbols in conjunction with the dereferencing operator ->*

> FIELD-SYMBOLS: <fs> TYPE n LENGTH 5.

> ASSIGN gr_v1->* TO <fs>.

> <fs> = 1111.

Are you trying to do something specific, or just understand how CREATE DATA works?

matt

[Former Member]

HI Marty

change the type of the gf_v1 to integer ( TYPE I )

do like that

data gf_v1 type I.

instead of

data gf_v1 type n length 5.

it works.

Thanks!

[matt]

>

> it works.

No it doesn't.

[Former Member]

This message was moderated.

[Former Member]

when i reading the abap objects book, i understand what the create data doing.

But when i implementation it, i don't know.........

[matt]

You use CREATE DATA usually when you don't know the type of the data you are using until run time.

If you are a beginner, leave it for now, and come back to the issue when you've thoroughly learned the basics.

matt

[Former Member]

i know, what create data to do, but i can't to use it.

[matt]

>

> i know, what create data to do, but i can't to use it.

Your initial post shows clearly that you don't fully understand. You've already been given some examples. ( Ignoring the one that's just wrong ).

Last chance:

>create data gr_v1 like gf_v1.

Creates a place in memory with the same shape as the variable gf_v1. gr_v1 then contains a reference to / a pointer to / the address of that place in memory.

Comment out your line "gr_v1 = 1111." and when you get to the debugger, look at the value of gr_v1. You'll see it contains reference data - not numerical character data.

Simply- your program doesn't pass syntax check because you are trying to assign numerical character data to a reference variable. You can only assign references to reference variables.

If doesn't work because you can't assign numeric character data to a reference variable. You can only assign references to reference variables.

As previously stated:

To get to the actual value you have to use field symbols in conjunction with the dereferencing operator ->*

> FIELD-SYMBOLS: <fs> TYPE n LENGTH 5.

> ASSIGN gr_v1->* TO <fs>.

> * <fs> = 1111.*

Do you understand now?

matt

[Former Member]

aha........ok......

now i try again

data gv_v2 type ref to i.
data gv_type type c length 1 value 'I'.
data gv_v1 type i.
field-symbols <fs> type any.

start-of-selection.

  gv_v1 = 1111.

  create data gv_v2 type (gv_type).

  ASSIGN gv_v2->* to <fs>.

  <fs> = gv_v1.

  break-point.

end-of-selection.

when i change the value from <fs>, it will be change by gv_v2->* too, but doesn't change by gv_v1

[matt]

That's right. gv_v1 and <fs> are separate objects.

But try this:

data gv_v2 type ref to i.
data gv_type type c length 1 value 'I'.
data gv_v1 type i.
field-symbols <fs> type any.
 
start-of-selection.
 
  gv_v1 = 1111.

  GET REFERENCE OF gv_v1 INTO gv_v2.
 
  ASSIGN gv_v2->* to <fs>.
 
  <fs> = '2222'.
 
  break-point.

[Former Member]

now, that is it, what i want show you.

 
data gv_v2 type ref to data.
data gv_type type c length 1 value 'I'.
data gv_v1 type ref to i.
data gv_v3 type i.
field-symbols <fs> type any.

start-of-selection.

  gv_v3 = 1111.
  create data gv_v1.
  gv_v1->* = gv_v3.

  create data gv_v2 type (gv_type).
  gv_v2 ?= gv_v1.
  break-point.

end-of-selection.

by debugging, when i change the value from gv_v1->*, it won't be change by gv_v3. why?

the reference point of the memory from gv_v3, or?

[Former Member]

Is gv_v1 new variabl?