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Tip of the Day
Language: Visual FoxPro
Expertise: Beginner
Jan 21, 2000

Passing a Variable to a Compiled Program

Question:
I am calling an .FXP from a batch file, but would like to pass a variable. Am I able to do this? How would FoxPro recognize it?

Answer:
You can put a PARAMETERS statement at the top of the PRG file to trap parameters used when calling a program.

For example, let's say that you have a program called GeneralLedger.prg for which you want to pass the name of the month to run the general ledger accounting program. At the top of GeneralLedger.prg, put the following:

 
PARAMETERS tcMonthName
IF PCOUNT()=0
   *-- no parameter passed, alert user and end
   MESSAGEBOX("Error: Please pass the name of the month")
   RETURN
ELSE   
   MESSAGEBOX("Running GL for "+tcMonthName)
ENDIF
 
Next, compile GeneralLedger.prg into an FXP file and put the following into the batch file:
 
GeneralLedger.fxp January
 
When you run the batch file, you will see a message box that says, "Running GL for January."

There is an important thing to be aware of. When you use a PARAMETERS statement to capture parameters passed from outside VFP, the parameters can only contain character information. For example, if the batch file were the following:

 
GeneralLedger.fxp 12345
 
the value of tcMonthName would be the string value "12345," not the numeric value 12345. What this means is that if you need the parameters to be anything other than characters, you will need to convert the passed character information into the required type. For example, let's extend the GeneralLedger program so that it can accept a month name and the year to run the GL:
 
PARAMETERS tcMonthName,tcYear

DO CASE
   CASE PCOUNT()=0
      *-- no parameter passed, alert user and end
      MESSAGEBOX("Error: Please pass the name of the month and the year")
      RETURN
   CASE PCOUNT()=1
      *-- one parameter passed, alert user and end
      MESSAGEBOX("Error: Please pass the name of the month and the year")
      RETURN
   OTHERWISE
      *-- Convert tcYear to Numeric
      lnYear = VAL(tcYear)
      MESSAGEBOX("Running GL for "+tcMonthName+', '+STR(lcYear))
ENDIF
 
Notice how the code translates the second parameter (tcYear) to a numeric using the VAL() function. If the batch file contained the following:
 
GeneralLedger.fxp January 2000
 
you would see a message box that says, "Running GL for January, 2000."
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