QuickTest was my introduction to VBScript. I think and dream in Perl, but I am coming around to a point where I can enjoy coding in VBScript. One of my biggest VBScript annoyances early on was the inability to define optional arguments for my functions.As I said, I think in Perl, so I set about trying to find a solution similar to how I pass arguments to subs in Perl. In Perl, I like to name my arguments, so I pass an array of arguments that the sub collects into a hash as named values. The syntax looks something like this.

I found an article on 4guysfromrolla.com about using optional arguments in VBScript. It suggests passing an array of arguments to the function. This is a good first step, but I don't like having to remember which value is which in the array. I still wanted my named arguments. Obviously I couldn't use a hash for this, so I used VBScript's nearest data type: a dictionary object. Once I have my parameters in a dictionary object, I can call them by name using syntax like oOptions("optionname"). The question was how to easily get all my options in a dictionary object.

I came up with a function I call DictBuild (insert platypus-related humor here). It takes an array and turns it into a dictionary object. The first value in the array is a dictionary element, the second value is that element's value, third - element, fourth - value...and so on. Basically, all even numbered values are dictionary elements and the odd value after each element name is its value.

This allows me to easily build a dictionary object with all my parameters.

Now this is finally becoming something I can work with, but what about defaults for these parameters? This is where my next function comes in: GetOpts. GetOpts takes two arrays as arguments and returns a dictionary object. The first array is the default values for the function. The second array is the custom options array that was passed to the function. GetOpts starts by building a dictionary object from the defaults array. Then it overwrites the default values with the custom options array if they exist. I also wrote some discipline for myself into GetOpts. If a option isn't listed in the defaults, it won't make it into the final dictionary.

So, now my function looks like this:

I think that about does it for my method of using named optional arguments in VBScript functions. I should note that I only use this for optional arguments, I put the variable names directly in the function signature for required values. So one of my real function delcarations looks like

The code for BuildDict and GetOpts is here:

Technorati Tags: VBScript, Quicktest Pro, Software Inquisition, Software Testing