Hi Kevin
Message: 4
Date: Mon, 26 Jun 2006 08:11:23 -0400
From: Kevin Cully <[EMAIL PROTECTED]>
Subject: Strong parameter checking
To: [EMAIL PROTECTED]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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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