xbasic code to read through a data file

[rrego]

i like to read a file in xbasic and change a few fields.
basically my code in Clarion is this

Open(filename)
loop until eof(filename)
next(filename) ! GETS THE NEXT RECORD
if field1 = '' then field1='N'
if field2 = '' then field2 ='N'
put(filename) ! writes record changes to the table
end
close(filename)

quite simple but just getting my feet wet with xbasic.

thank you
Raul Rego

[Clunes]

Re: xbasic code to read through a data file

Are you wantting open a text type file or are you wanting to edit a table

[Stan Mathews]

Re: xbasic code to read through a data file

Since files other than tables don't have fields, let's assume you mean a dbf table.

tbl = table.open("filename") 'Open(filename)
tbl.fetch_first()'goto first record
while .not tbl.fetch_eof() 'loop until eof(filename)
'nothing here, haven't processed the first record yet, don't want to move to the second record 'next(filename) ! GETS THE NEXT RECORD
if tbl.field1  = "" 'if field1 = '' then field1='N'
tbl.change_begin() 'begin the change
tbl.field1 = "N"
tbl.change_end (.T.) 'commit the change
end if
if tbl.field2 = "" 'if field2 = '' then field2 ='N'
tbl.change_begin()
tbl.field2 = "N"
tbl.change_end(.T.)
'nothing here, performed with .change_begin() and .change_end() methods 'put(filename) ! writes record changes to the table
tbl.fetch_next() 'now move to the next record
end while 'end
tbl.close() 'close(filename)

[Tom Cone Jr]

Re: xbasic code to read through a data file

Raul, there are a number of xbasic examples in the programming puzzles I've been posting to the General Questions Forum. You may find them useful as you climb the xbasic learning curve.

[Ray in Capetown]

Re: xbasic code to read through a data file

Nice Stan, and see, you dont do all that work for nothing - I'm also paying attention

tbl = table.open("filename") 		'Open(filename)
tbl.fetch_first()'goto first record
while .not tbl.fetch_eof() 		'loop until eof(filename)
  if tbl.field1  = ""			
	tbl.change_begin() 		'begin the change
	tbl.field1 = "N"
	tbl.change_end (.T.) 	        'commit the change
  end if
  if tbl.field2 = "" 
	tbl.change_begin()
	tbl.field2 = "N"
	tbl.change_end(.T.)
  [COLOR="#FF0000"]end if[/COLOR]
  tbl.fetch_next() 'now move to the next record
end while                                    'end
tbl.close()

[Stan Mathews]

Re: xbasic code to read through a data file

Thanks Ray.

[Tom Henkel]

Re: xbasic code to read through a data file

My question here is "why wouldn't you do an "UPDATE" operation?" and set the condition on the field? I like writing xbasic as much as the next one, but the tools are there for those who don't want to write the code.

Tom

[Stan Mathews]

Re: xbasic code to read through a data file

Good point, Tom but I think he's trying to learn xbasic. It could have been pointed out that Alpha has easier ways to accomplish the end result.

[CALocklin]

Re: xbasic code to read through a data file

I'm coming to this a bit late but there is no need to start the change twice. A simple test on a simple table indicated that it took about 60% longer that way - assuming both fields need to be changed. The difference could be a much greater than that if there are a lot of records and/or indexes because A5 will update any affected indexes every time a change ends. (Unless you use batch_begin/end() but that's another story.)

Also, just an FYI, there is nothing wrong with using the .T. in the change_end() but it isn't necessary - it's the default anyway. The only real advantage I've ever found for using that argument is when I want to use a "save_flag" variable for development purposes so I can run the routine for debugging without actually saving any data. If there is a need to decide whether or not to save something in the finished routine, that can be done before starting the change/enter in the first place.

When I use a save_flag I put it at the top of the script so it's easy to find. In other words...

save_flag = .F. 'set to .T. before distributing.
...
tp.change_end( save_flag )
...
tpd.change_end( save_flag )
...

Of course, I generally only use a save flag on longer scripts where there are multiple possible change/enter operations. It doesn't make much sense on short scripts with only one change/enter .

Here's my method:

tbl = table.open("filename")         'Open(filename)
tbl.fetch_first()     'goto first record
WHILE .not. tbl.fetch_eof()         'loop until eof(filename)
    IF tbl.field1 = "" .or. tbl.field2 = ""
        tbl.change_begin()         'begin the change
        IF tbl.field1 = ""
            tbl.field1 = "N"
        END IF
        IF tbl.field2 = ""
            tbl.field2 = "N"
        END IF
        tbl.change_end()
    END IF
    tbl.fetch_next()     'now move to the next record
END WHILE 'end
tbl.close()

[rrego]

Re: xbasic code to read through a data file

My question here is "why wouldn't you do an "UPDATE" operation?" and set the condition on the field? I like writing xbasic as much as the next one, but the tools are there for those who don't want to write the code.

Tom

Tom, thanks. I sort of want to learn Xbasic. In Clarion it was easy to learn the language because as I created a screen or browse in GUI, Clarion generated the code; this doesnt seem to be the case in Alpha unless I am missing something obvious.

BUT, getting back to the learning process, how do you use "UPDATE"?

thanks

[Ray in Capetown]

Re: xbasic code to read through a data file

You do the same to create a screen or browse - in GUI
What you want to do is an operation on data in a table.

In the Control Panel, click tab OPERATIONS, select NEW, choose type of operation - Update Records
Select the table you want to use and fill in the rest.
The code that is produced, if you wish, is also available

You may want to do some reading and try stuff out first as much as possible, otherwise answers to your questions could become a long slow tutorial. Try to use the Interactive window, and the help examples provide code snippets.

and Welcome.

[DB_Dan]

Re: xbasic code to read through a data file

Raul, there are a number of xbasic examples in the programming puzzles I've been posting to the General Questions Forum. You may find them useful as you climb the xbasic learning curve.

Tom. How about a link(s) to what you've posted in the GQF section. I could really use some end-to-end examples for web-based Alpha v11 applications.

By 'end-to-end' I mean What type of object to create; Which object options to click; Where to paste the Xbasic code?

Thank you!

[Tom Cone Jr]

Re: xbasic code to read through a data file

Daniel,

The Programming Puzzles forum was created after the post you reference. The message board folks moved my puzzles from the GQF to the Programming Puzzles forum, not sure what links you now would like to see?