The LA Fox Developer Newsletter

October 1999

FoxPro Q&A

Q. I would like to add the button ‘Dial’ to my VFP grid with

names and telephone numbers. After pressing the dial-button

my modem should dial the number.

Al. If you are working on NT or Win95 you can use

MSCOMM32.OCX that ships with VFP.

A2. MSCOMM32.OCX only installs if your running Win95 or NT,

not on Windows 3.1. If so, try this routine using the Window

API. It works well under 3.1, pretty stable on 95 & NT. You’ll

need to provide the parameters starting with THISFORM.

*

write data to the serial port.

SET LIBRARY TO ‘FOXTOOLS.FLL’

*

Assumes that the number to dial is stored in

ThisForm.CallNumber

M.Output = “ATDT” + ThisForm.CallNumber + PAM + CHR(13)

LOCAL Iccomport, lcdstring, Inport,

Iccomport = LEFT(THISFORM.ComPort,4)

Icdstring = m.output

OPENCOMM = REGFN(”OPENCOMM”,’CIl”,”l”,’USER.EXE’)

WRITECOMM = REGFN(’WRITECOMM’,’ICI’,’I’,USER.EXE’)

CLOSECOMM = REGFN(’CLOSECOMM’,’I’,’I’,’USER.EXE’)

open comm port

LNPORT = CALLFN(OPENCOMM,LCCOMPORT,1 00,100)

x = SECONDS()

DO WHILE SECONDSO . X <1

ENDDO

send string to modem

=CALLFN(WRITECOMM,LNPORT,LCDSTRING,LEN(LCDSTRING))

mTlmø = SEC.OP4DS()

**

wait for KeyPress or timeout

DO While INKEY(”HM”) =0 AND SECONDSO - mTime <15

ENDDO

hang up modem

M.Output = PATHOAMP + CHR(13)

=CALLFN(WRITECOMM,LNPORT,LCDSTRING,LEN(LCDSTRING))

=CALLFN(CLOSECOMM,LNPORT)

x=SECONDS()

DOWHILESECONDSQ-X<2

ENDDO

RELEASE LIBRARY ‘FOXTOOLS’

(Ed Vanduyne, CIS ID: 75740,3071)

*

save the file

Endif

Q. What is the scope of an Include file?

Al. When you include a file in a form using the Form/Include

File menu item, all objects of the form have access to the

contents. If you explicitly #include it in a method, only that

method has access to it. In the class designer, the same rules

apply. But you don’t have an easy way to have VFP include the

same file in all classes stored in the classlib, it has to be

specified on a class by class basis. No you don’t “inherit”

include file contents. For a subclass you need to do is create a

.h file for the subclass and then #include the parentclass’ .h file

first and then add the #deflnes for the subclass. Something

along the lines:

create class inc1 of inctest as custom

*

this class has an include file inc1.h

*

inci.h

#define x I

create class incla of inctest as inc1 from inctest

*

this class has an include file inc1a.h

*

inc1a.h

#include incl.h

#define y 2

otherwise inc1 a would not be able to use the #deflned x item.

It’s far from perfect, if the parentclass include filename changes

the subclasses get broken, but it’s the only way you can do it.

What I generally do with classlibs is create a single

ClassLibName.h file and every class stored in that classlib that

needs an include file puts it’s contents in the single file. For

application level stuff I create a single AppName.h file and

include that on all the forms and prgs. And AppName.h #in-

cludes any necessary .h files for the classlibs plus the app

specific stuff.

(David Frankenbach, CIS ID: 72147,2635)

Q. I am allowing the user to specify the name of a file. I am

using PUTFILEO to allow the user to enter the name, but when

they select a file that always exists, I always get a warning

about overwriting the file. This happens no matter the setting of

SET SAFETY. Is there an option?

Al. PutFile() invokes the standard windows Save Dialog. One

way around this is to use the common dialog OCX control. By

placing the OCX control on a form, you can invoke the

ShowSave() Method of the control. If you elect to choose a file

that already exists, a dialog *wiIl not* appear. Once you have

made a file selection, this will update the FileName Property

of the OCX control:

ThisForm.OleControll .ShowSave()

If NOT Empty(ThisForm.OleControll.Filename)

Q. How can I implement an automatically incrementing primary

key?

A. The most foolproof way I can find, and I’ve tried many, is to

use a “system” table that stores the most-recently incremented

number for each field. I have a GetPKey() function that will lock

the record in the system table, increment the number, unlock

the record and return the number. If I wanted to, GetPKey()

could be used as the default value for the field in the database. I

choose not to do so for many reasons, but that is the simplest

way to “autonumber” in VFP, IMHO. It would be nice if this were

a built-in feature of the VFP engine as there are many draw-

backs to the “roll your own” techniques required now. For

example, functions for default values don’t work via ODBC.

(Con’t, page 9)

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