The work-around
|
Interested in Using Optional Parameters in JScript?
If you use JScript as your server-side scripting language, you may be
wondering if (and how) you can use optional arguments. Fortunately, JScript
allows this use natively, so you don't have to use any tricks like with VBScript.
However, the syntax for using optional arguments in JScript is a bit non-intuitive.
To learn more, click here.
|
One method for simulating optional arguments in VBScript that has not been
discussed in any 4Guys article, though, is the use of the class-as-function-call
method. This method is very popular with component developers. You could say
that SoftArtisan's
entire FileUp component is one class-as-function call. What I mean by this is
instead of saying something like this (which VBScript won't even allow but VB
and C++ do):
function ComputeNodePathHtml(theNode,
showImage = true, showLinks = true, forceVerdana = true, ...)
...
end function
|
To use a class-as-function call, we first need to create a class. This is
a feature that VBScript started supporting back in version 5.0. To learn what
version of VBScript you are running, check out: Determining
the Server-Side Scripting Language and Version.
To utilize the class-as-function method, our class should contain a member
variable for each parameter. Each function and subroutine that supports optional
parameters should accept zero parameters. While this may seem a tad confusing,
check out the code below, which will (hopefully) clear everything up!
class NodePathHtmlGenerator
Dim theNode
Dim showImage
Dim showLinks
Dim forceVerdana
function RenderHtml
if IsEmpty(showImage) then showImage = true
if IsEmpty(showLinks) then showLinks = true
if IsEmpty(forceVerdana) then forceVerdana = true
...
end function
end class
|
To call this function simply create an instance of the class, set whatever
properties you care to, and then call the main method:
Dim node_path_obj
Set node_path_obj = new NodePathHtmlGenerator
Set node_path_obj.theNode = the_node
Response.Write node_path_obj.RenderHtml
|
Of course the above approach is three lines longer than it could be, but once
you're commonly using more than a couple parameters (and not often using
more than a few other parameters), the clarity of named parameters outweighs
the extra typing.
To ensure that the properties were of the correct data type and format, you'd
likely want to create the class's properties as Private and then
use Property Let and Property Get statements to read
and write the values, respectively. Also note that you can have more than one
function or subroutine in the class. Just be sure to create class properties
for each of the optional parameters that each function or subroutine may need.
Happy Programming!