FoxPro and Include Files

Constants

If you know that in the normal course of events some things (values) will not change during program execution, many advantages can be found by assigning these values to variables and storing them in an ‘include’ file, then including the file (in various ways) at strategic points within the program.

One advantage is that with careful naming these variables will enhance the readability of your codes.

By way of example

Consider the following two short snippets of code:

IF MESSAGEBOX("Save Record",32+4,"Confirm")=8
    {do something that saves the record}
ENDIF

IF MESSAGEBOX("Save Record",gc_Question+gc_YesNo,"Confirm")=gc_Yes
    {do something that saves the record}
ENDIF

I think you would agree that the 2nd section of code is easier to understand. However this could be somewhat tedious if you had to declare the variables every time you wished to use them in this manner.

FoxPro (and other languages) allows you to store declared variables in an external file (called an ‘include’ file) and then insert its content at various locations in the program.

Creating an Include File

Include files in general are simply plain text files which contain the definition of predefined variable names and their associated values.

In Foxpro these files usually have a .h or .prg extension. I myself tend to use the .prg, simply so that I do not have to remember to use .h, since VFP by default uses .prg for its extension to command definitions.

Constants.prg

To create an include file called constants using VFP do the following:

From the command window issue

Modify command constants

Then enter the following lines of text and save the file.

*: CONSTANTS
*; Value Dialog box buttons
#DEFINE    gc_OKOnly 0            &&    0    OK button only.
#DEFINE    gc_OKCancel 1            &&    1    OK and Cancel buttons.
#DEFINE    gc_AbortRetryIgnore 2        &&    2    Abort, Retry, and Ignore buttons.
#DEFINE    gc_YesNoCancel 3        &&    3    Yes, No, and Cancel buttons.
#DEFINE    gc_YesNo 4            &&    4    Yes and No buttons.
#DEFINE    gc_RetryCancel 5        &&    5    Retry and Cancel buttons.

*;Value    Icon
#DEFINE    gc_stop 16            &&    16    Stop sign.
#DEFINE    gc_Question 32            &&    32    Question mark.
#DEFINE    gc_Exclamation 48        &&    48    Exclamation point.
#DEFINE    gc_Information    64        &&    64    Information (i) icon.

*;     Value    Default button
#DEFINE    gc_1st_button    0        &&    0    First button.
#DEFINE    gc_2nd_button 256        &&    256    Second button.
#DEFINE    gc_3rd_button 512        &&    512    Third button.

*; Return Values
#DEFINE    gc_OK 1
#DEFINE    gc_Cancel 2
#DEFINE    gc_Abort 3
#DEFINE    gc_Retry 4
#DEFINE    gc_Ignore 5
#DEFINE    gc_Yes 6
#DEFINE    gc_No 7

Including an Include File

Once you have created your include file(s) you can then insert them at strategic places within you source code.

Much depends on exactly what you are trying to do, and the scope (how long they remain in existence) of the defined variable in question.

In its simplest form a file can be included in another .preg file by an include declaration

#INCLUDE constants.prg

This will tell foxpro to ‘include’ the declaration at this point in the program, and then they will be available (within that program) to use until the program ends at which time they will cease to exist.