INFO: Use Place-Holder Commas in Calls with Missing Parameters (131549)
The information in this article applies to:
- Microsoft Visual FoxPro for Windows 3.0
- Microsoft Visual FoxPro for Windows 5.0
- Microsoft Visual FoxPro for Windows 6.0
This article was previously published under Q131549
3.00
WINDOWS
SUMMARY
This article shows by example how to pass parameters to functions,
procedures, or methods by using place-holder commas for empty values that
will take a default value. When you pass nothing, the function receives
false (.F.) as the value for that argument.
This Visual FoxPro behavior is different from the behavior of FoxPro
version 2.6. In FoxPro version 2.6, you could pass fewer arguments than
total number of parameters only if the blank arguments came after the valid
(full) arguments.
MORE INFORMATION
In Visual FoxPro version 3.0, you can pass fewer arguments than are
requested by a function, method, or procedure by using place-holder commas
when you call it.
Code Sample
To demonstrate passing blank parameters, copy the following code into a
program file called FOXTEST.PRG and run it:
*** BEGINNING OF SAMPLE CODE ***
*****************************************************************
* FOXTEST.PRG *
* Demonstrates How Visual FoxPro Allows Passing Blank Values *
* For Parameters Anywhere In the Parameter List *
* *
*****************************************************************
SomeDate = mydate(3,4,95) && Pass values for all parameters
WAIT WINDOW SomeDate
SomeDate = mydate(4,,94) && Pass blank values for 2nd parameter
WAIT WINDOW SomeDate
SomeDate = mydate(,4,) && Pass blank values for 1st and 3rd
WAIT WINDOW SomeDate && parameters
SomeDate = mydate(,,94) && Pass blank values for 1st and 2nd
WAIT WINDOW SomeDate && parameters
SomeDate = mydate(4,,) && Pass blank values for 2nd and 3rd
WAIT WINDOW SomeDate && parameters (This is the only way FoxPro
&& 2.x allowed blank values to be passed,
&& at the end of the parameter list only.)
PROCEDURE MyDate
PARAMETERS Month,Day,Year
* Give each variable a default value for the missing parameters.
DO CASE
CASE TYPE("Day")="L"
lcday="01"
CASE TYPE("Day")="N"
lcday=ALLTRIM(STR(DAY))
ENDCASE
DO CASE
CASE TYPE("Year")="L"
lcyear="95"
CASE TYPE("Year")="N"
lcyear=ALLTRIM(STR(Year))
ENDCASE
DO CASE
CASE TYPE("Month")="L"
lcmonth="01"
CASE TYPE("Month")="N"
lcmonth=ALLTRIM(STR(Month))
ENDCASE
RETURN lcmonth+"/"+lcday+"/"+lcyear
*** End Of Sample Code ***
REFERENCES
For more information about passing parameters in a parameter list, refer to
the Visual FoxPro Help file, "Parameters Command" topic.
| Modification Type: | Minor | Last Reviewed: | 3/3/2005 |
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| Keywords: | kbcode kbinfo KB131549 |
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