XBasic code indirection: setting field values

[MS]

Hi folks,

I was looking at the 'Code Indirection' example in the manual and rather than setting variables to the values in fields, I was trying to go the other way round.

My script works if I name each variable-field pair explicitly e.g.
t.Company = cCompany
t.StartDate = dStartDate etc
...but if I try to refer to them indirectly as in the manual example, I get an assortment of errors (var mismatch etc) depending on what code I try. I have searched and searched for an example but cannot find one. I know I should teach myself how to use the debugger, and I will, but in the meantime, any help would be greatly appreciated.

I will be happy to post my code, but it might be easier just to work from a slightly modified version of the example in the book which for your convenience is below. Note also that I am trying to do this for a series of records, not just one as in the book, hence the need to amend the example code slightly.

Thanks for your time.
MS


CODE INDIRECTION EXAMPLE FROM THE MANUAL
'Next line removed as my script is not a function
'function xlookup as L(tablename as C, rec as N)
'Next line added as example did not specify the table
tablename = Table.actual_filename_get("cleaner upper")
t = table.open(tablename)
t.index_primary_put()
'Next line changed to point to 1st rec
t.fetch_first()
num_fields = t.fields_get()
'Next two lines added to handle multiple recs
for rec = 1 to 20
t.change.begin()
for I = 1 to num_fields
f = t.field_get(I)
evaluate_template("dim global " + f.name_get() + " as " + f.type_get())

eval(f.name_get()) = f.value_get()
next I
'Next two lines added line to close the multiple recs 'for' loop
t.change.end(.t.)
next rec
t.close()
end function

[Tom Cone Jr]

RE: XBasic code indirection: setting field values

MS,

Not clear on what your goal is. i.e. don't know what you mean by 'the other way round'.

If you have values stored in variables and you want to assign them to fields in your table you can do it directly, without any indirection being necessary.

Assigning to fields in new records would use the routines described for tbl.enter_begin().

Assigning to fields in existing records would include script commands to navigate to the desired records, one at a time, and then tbl.change_begin().

If you want to update the same fields in a range of records in your table, using values stored in variables, i suggest you define an update operation.

BTW, local custom is for real names to be used instead of handles or initials. You might want to re-register in the forum.

-- tom

[Peter.Wayne]

RE: XBasic code indirection: setting field values

if you are trying to set fields to variables, then your code should be

eval("t."+f.name_get()) = something
or more simply
f.value_put(something) -- the eval() function is not needed.

you have written
eval(f.name_get()) = f.value_get()
which should set variables to the values in fields. notice your code repeatedly resets the same variables to new values as it scrolls through the records. you don't need the change_begin() and change_end() in your script since you're not actually changing anything in the table.

[Lenny Forziati]

RE: XBasic code indirection: setting field values

BTW, local custom is for real names to be used instead of handles or initials. You might want to re-register in the forum.

There is no need to re-register to change your name that is displayed. Simply click the "Modify Your Preferences" link that is on the bottom of every page and update your name.

-Lenny

[MS]

RE: XBasic code indirection: setting field values

Gentlemen,

thank you for your responses.

Tom, I will set up a 'real-name' account shortly but will continue as is here for continuity on this thread. Apologies for that legacy from when I first started looking at Alpha and didn't know them from Spam Inc.

Peter, the line you suggest of...
eval("t."+f.name_get()) = something
...was one of the three I had narrowed it down to. Thank you for providing certainty.

Everything works beautifully now. That said, I do have one very small question:

The .pdf and .chm help files will not let me search for "var->", so...
If we have a variable called, say, firstname, what, if any, is the difference between...
var->(firstname)
...and....
eval(firstname)

Thanks again.
'MS'