>Keith-
>
>>An important item that may be overlooked is that using dodefault(
) effectively breaks pcount().
>
>That's interesting. I've never run up against it with PCOUNT(). I wouldn't use PARAMETERS(), of course. That _does_ break. Do you have an example for PCOUNT()? I, for example tried it with keypress in the spirit of the thread and found it *seemed* to operate fine.
Nancy,
I recently modified one of my apps by adding code to a method in one of the classes. The method had been defined in a parent class and expected 3 or 4 parameters - the last is optional.
When I added the code, I used DODEFAULT(param1, param2, param3, param4) because I saw that 4 parameters were in the auto-generated LPARAMETERS line. Of course, the program exhibited some unexpected behavior. When I traced through the code, I saw that I was using PCOUNT() in the original class.
Passing the original paramaters through with DODEFAULT() didn't work because the 4th parameter comes through as .F. when there is not a corresponding parameter in the original call. When the .F. is passed up the chain, the receiving methods see 4 parameters, not 3:oParentTest = createobject('MyClass')
oParentTest.Testit('This is a test')
oTest = createobject('MyChildClass')
oTest.Testit('This is a test')
release oTest, oParentTest
define class MyClass as custom
procedure Testit
lparameters p1, p2
wait 'P1:'+vartype(p1)+':'+transform(p1) window
if pcount() > 1
wait 'P2:'+vartype(p2)+':'+transform(p2) window
else
wait 'P2: No parameter passed' window
endif
endproc
enddefine
define class MyChildClass as MyClass
procedure Testit
lparameters p1, p2
dodefault(p1, p2)
endproc
enddefineFrom this example you can see that in order to obtain the correct results, we would have to test for the existance of parameters in the child method before calling the parent with dodefault():define class MyChildClass as MyClass
procedure Testit
lparameters p1, p2
do case
case pcount() = 0
dodefault()
case pcount() = 1
dodefault(p1)
otherwise
dodefault(p1, p2)
endcase
endproc
enddefine
So we have some choices as a developer:
1. Never use optional parameters in our custom methods
2. Always use a do case..endcase when using dodefault()
3. Always test the count and type of all parameters in every public method before using them AND write some error handling code if they don't match, which could break when dealing with logical parameters.
