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VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 3:58:23 AM

humbletech99

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I was wondering if there was some way that I can write a function or sub that can be called with or without arguments?

I specifically want to be able to write a func/sub that can either accept 1 or 0 arguments and then handle that inside the func/sub to respond differently.

I suspect that the best I can do is pass in an empty string, but I'd be happy to hear anyone's wisdom on this?

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 4:37:55 AM

ebgreen

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VBScript does not support the concept of optional args, so you can't explicitly do what you want. On the rare occasion that I have needed to have optional parameters I have handled it with either a dictionary (named parameters essentially) or an array (order specific parameters essentially).

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 4:39:23 AM

ehvbs

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Hi humbletech99,

the VBScript Docs list "ParamArray" as "VBS feature not supported in VBScript". So
you can't define a function, method, or sub that can be called with a different number
of arguments.

If you use one (or more) scalar variable(s) in your argument list, consider using
Empty for 'unused' parameter(s); e.g.

   doWhatIWant Empty
   doWhatIWant ""
   doWhatIWant "asap"

Another strategy is to pass one array - or dictionary - to the sub/function/method; e.g.

   sRes = sprintf( "no %% in here!", Array() )
   sRes = sprintf( "%d %s in here!", Array(1, "string" ) )

For a "zero or one" szenario, even defining two functions/subs/methods, would be
worth of discussion too.

Regards

ehvbs

(in reply to humbletech99)

Post #: 3

RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:05:00 AM

humbletech99

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could you actually get away with defining two functions of the same name to try to overload the function name and catch it whether it is called with 1 arg or no args?

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:07:55 AM

ebgreen

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VBScript does not support overloading either.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:10:27 AM

ehvbs

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I wrote:

For a "zero or one" szenario, even defining two functions/subs/methods, would be
worth of discussion too.

but wanted to say:

For a "zero or one" szenario, even defining two functions/subs/methods with
different names (of course), would be worth of discussion too.

(in reply to ebgreen)

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:17:26 AM

humbletech99

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well it's 4 functions that I want to behave like this so I'd rather not suddenly have 8 functions with significant redundant code....

I actually thought you were talking about function name overloading...

ps. I think you meant to spell that "scenario"?

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:32:18 AM

Rischip

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One way to simulate overloading is to send in a single argument which is delimited.
Have the routine split on the delimiter and count the number of arguments.
you could internally "typecast" the indivdual variables if necessary based on position.
It might be difficult to figure out if you are trying to send object as arguments, but simple strings and numbers should be easy.

< Message edited by Rischip -- 1/30/2008 5:33:31 AM >

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:39:16 AM

ebgreen

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Good point Rischip. I had forgotten delimited strings. The only reason that I would prefer an array or dictionary over a delimited string is that it is more generalized since I don't have to worry about the delimiter being in one of the arguements and throwing everything out of whack.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:46:32 AM

ehvbs

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Hi humbletech99,

code:

output:

Regards

ehvbs

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 5:58:52 AM

ebgreen

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Or as one function using an array:

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:04:14 AM

ehvbs

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Hi Rischip,

for some scenarios - e.g. when the parameters are short strings - writing them
in one literal string or joining them is ok. But given other circumstances - e.g.
when you need many arguments of different types - VBScript's lack of serialization/
loss of type information is a serious drawback of your method.

The dictionary approach would give some kind of named parameters (no need to
memorize the order of arguments). But setting up the dictionary is clumsy.

So I think, putting the arguments in an array is the solution for most seasons.

Regards

ehvbs

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Post #: 12

RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:07:16 AM

ebgreen

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Here is the one function dictionary:

As ehvbs pointed out, the setup for the dictionary method is trickier than the array. The array is the method that I most often use, however if the data being passed into the function is sufficiently complex I think the dictionary methods has the potential to be more clear.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:20:03 AM

Rischip

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I agree delimited may not be the answer, but what I was going for was a single argument that could be parsed.
A dictionary has one drawback which is it only stores unique items. So it could be painful to assign and retrieve items.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:24:10 AM

ebgreen

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Could you elaborate on this?

"A dictionary has one drawback which is it only stores unique items. So it could be painful to assign and retrieve items. "

I'm not sure that I understand.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:29:21 AM

ebgreen

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Just for completeness, the delimited string method:

Notice that the delimited string method is really the same as the array method with the array creation moved into the function.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:32:34 AM

ehvbs

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Hi Rischip,

I think "unique items" is a pro of the dictionary approach; compare ebgreen's

dicArgs.RemoveAll
dicArgs.Add "Txt", "I will never write 'szenario' again!"
...
a second
dicArgs.Add "Txt", "and now something completely different!"
will throw an error
...
If dicIn.Exists("Fnd") And dicIn.Exists("Rpl") Then
improveEN = replace( dicIn("Txt"), dicIn("Fnd"), dicIn("Rpl") )

vs:

args = Split(argument,",",-1,1)
If 2 = UBound( args ) Then
improveEN = replace( args( 0 ), args( 1 ), args( 2 ) )

It's much more explicit/lucid/safe - but you pay for this feature. Sometimes your
method may well be more suitable.

Regards

ehvbs

(in reply to Rischip)

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:33:34 AM

Rischip

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dicArgs.Add item(0) must be unique as it is the key. So any routine creating the argument to pass would have to account for this.
I think in this instance the Array method would be best, as it can hold objects which would be (how should I say) impossible with a delimited string.

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RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:42:45 AM

ehvbs

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Hi ebgreen,

I think your

Notice that the delimited string method is really the same as the array method with the array creation moved into the function.

is easily misunderstood.

array creation <> splitting a string into an array
all datatypes <> strings only
can be nested <> is flat

Regards

ehvbs

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Post #: 19

RE: VBScript - Writing Func/Sub that can take 0 or 1 args? - 1/30/2008 6:42:56 AM

ebgreen

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I agree that I usually use the array method just due to it's simplicity.

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"... when you are good and crazy, oooh, oooh, oooh, the sky is the limit!" - The Tick
Goog places to start:http://www.visualbasicscript.com/m_24727/tm.htm
http://www.visualbasicscript.com/m_47117/tm.htm

(in reply to Rischip)