In terms of 'tightly coupled' vs 'loosely coupled' (to use old terms)
code, we're now more inclined towards passing parameters to modules
versus having modules be aware of their environment. That's a good
thing, but it increases the number of parameters being passed around,
which could - if the caller is not to be trusted - have the effect of
requiring considerable code to inspect parameters in each called method.
In any case, my own practice is have some checking of parameters (e.g.
pcount), but mostly to aid developers from making mistakes, not to
thwart intentional misuse. From that side of the coin, I'd look to
global resource protection mechanics and not even think about trying to
make every module "secure".
Bill
> > I'm working on a class that I'm wanting to make Open Source and I'm
> > making functions/methods that take parameters. This
> function could be
> > abused in ways that I have never anticipated. Since VFP is loosely
> > typed, I'm wondering what checking I have to do on these
> parameters to
> > make sure that the parameter is provided, not .NULL. and of
> the type
> > expected? Is this overkill?
> >
> > FUNCTION MyFunction(tcSomething AS String) AS String
> > LOCAL lcRetVal
> > lcRetVal = []
> > IF PCOUNT() = 1
> > IF NOT ISNULL(tcSomething)
> > IF VARTYPE(tcSomething) = "C"
> > IF NOT EMPTY(tcSomething)
> > lcRetVal = [My Function ] + tcSomething
> > ENDIF
> > ENDIF
> > ENDIF
> > ENDIF
> > IF EMPTY(lcRetVal)
> > =MESSAGEBOX("Your call to " + PROGRAM() + " is lacking." + ;
> > " Try again."
> > ENDIF
> > RETURN lcRetVal
> > ENDFUNC
> >
> > What's the most graceful way in VFP to accomplish this?
> ASSERTS work
> > in development but what about data driven production
> systems? There
> > must be a better way that I'm unaware of.
>
> Personally I find it easiest to check parameters first and
> get out if necessary and then follow with the heart of the
> function. This clearly separates the two steps and the meat
> of the function is cleaner and easier to follow.
>
> FUNCTION MyFunction(tcSomething AS String) AS String
> LOCAL lcRetVal
> lcRetVal = []
> IF PCOUNT() = 0 OR VARTYPE(tcSomething) # "C"
> RETURN lcRetVal
> ENDIF
>
> *Now the real meat of the function is not tabbed way over
> for nothing.
>
> RETURN lcRetVal
> ENDFUNC
>
> Mike
>
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