Mr. Script

Windows Script Components, Part Deux

The wizard is great, but you'll have to dig deeper to reap all of WSC's rewards.

This month, I'll continue my series on Windows Script Components. Last month, we used the Windows Script Component Wizard to create our very first Windows Script Component (WSC). The wizard handled all the plumbing, leaving us the simple task of defining our Properties and Methods. The next step is to add the code to the WSC.

We're Off to See the Wizard (And Fix His Mistakes!)
No doubt about it—the Script Component Wizard is a wonderful tool. Unfortunately, the skeleton component it creates is far from ready. The first thing you'll notice is that all the Properties have been set up as Procedural Properties (remember those?), each with corresponding Get and Put methods.

<public>
<property name="MyProp1">
<get/>
<put/>
</property>
<property name="MyProp2">
<get/>
<put/>

Because both of these properties are Read/Write and because I don't need to apply any logic in order to determine the values of these properties, I'll go ahead and change them to "normal" Public Properties.

<public>
<property name="MyProp1">
</property>
<property name="MyProp2">
</property>

Of course, you can save even more space by putting the XML terminating slash "/" on the same line.

<public>
<property name="MyProp1">
<property name="MyProp2">

Go ahead and delete the corresponding "get_xxx" and "put_xxx" methods from the <script> section, as these properties will be accessed directly.

Getting Hungarian?
You may have noticed that the Properties are referenced internally using their Public names. If you wish to use Hungarian Notation within your component (and you should), you need to add a reference to an internal name.

<public>
<property name="MyProp1" internalname="iNum1">
<property name="MyProp2" internalname="iNum2">

You also need to change the Dim statement inside the <script> section.

<script language="VBScript">
<![CDATA[

dim iNum1
dim iNum2

This is pretty cool! Remember that, in classes, the only way to use Hungarian Notation was to create Procedural Properties. WSCs allow you to avoid that added code and still use any internal name you wish. Ahh—the joys of XML! I'll also get rid of the default value of "True" for MyProp1 (AKA: iNum1), as I'm dealing with numbers now.

Now Let's Make It Do Something
The wizard created two Functions for my two methods. I'll fill in some code to do some simple math. Method 1 will change the values of MyProp1 and MyProp2. Because it won't need to return a value, I'll change it from a Function to a Sub. I'll also change the parameters to integers instead of strings. (Actually, all I've really changed is the Hungarian Notation. WSCs, just like VBScript, treat every variable as the type VARIANT.) Don't forget to also change this in the PARAMETER value of the Method's declaration line under <public>.

sub MyMethod1(iValue1, iValue2)
iNum1=iValue1
iNum2=iValue2
end sub

Method 2 will add the values of the two Properties. Because it'll be accessing the properties directly, I don't need to provide arguments. However, as it's returning a value (the sum of the two numbers), I need to leave it as a Function.

function MyMethod2()
MyMethod2 = iNum1 + iNum2
end function

Your Windows Script Component should now look like this. (Your GUID, of course, will be different!)

<?xml version="1.0"?>
<component>
<registration
description="MyScriptComponent"
progid="MyScriptComponent.WSC"
version="1.00"
classid="{7428c732-9472-422e-9878-bdca8433db0e}"
>

</registration>

<public>
<property name="MyProp1" internalname="iNum1">
<property name="MyProp2" internalname="iNum2">
<method name="MyMethod1">
<PARAMETER name="iValue1">

<PARAMETER name="iValue2">
</method>
<method name="MyMethod2">
</method>
</public>

<script language="VBScript">
<![CDATA[

dim iNum1
dim iNum2

sub MyMethod1(iValue1, iValue2)
iNum1=iValue1
iNum2=iValue2
end sub

function MyMethod2()
MyMethod2 = iNum1 + iNum2
end function

]]>
</script>

</component>

Is Any of This Registering With You?
The final step before using the new component is to register it. The easiest way to do this is to simply right-click the file in Explorer and select "Register" (Figure 1).

Registering WSCs
Figure 1. Windows makes registering WSCs extremely simple. (Click image to view larger version.)

Windows knows that WSC files are components, so it automatically gives you the option of registering it. For those who like doing things the manual way, you can still use Regsvr32.exe to do it.

C:\Regsvr32 path\component_name.wsc

Looking back at Figure 1, you can see that there's another option—Generate Type Library. This allows you to create a type library (.TLB file) so you can look at the component through an object browser like XRay.exe. This comes in handy once you've built up a repository of WSCs and need to look at a component to determine its interfaces. You create these type libraries one at a time, as the .TLB file created is always called "Scriptlet.tlb." (You can manually generate your .TLB file from a script and give it the appropriate name, but automatically generating it and then renaming it is easier!) Rename it to match the WSC's name and keep it in the same folder. Figure 2 shows the new component viewed inside XRay.

Generated type library
Figure 2. The generated type library lists the methods and properties, just like a normal component. (Click image to view larger version.)

Putting it to Work
Now that the component is registered, all that remains is writing a script to use it. The following script uses Method1 to set the values of the Properties and Method2 to display the sum.

' MathTest.vbs
Dim objWSC

Set objWSC=CreateObject("MyScriptComponent.WSC")
objWSC.MyMethod1 1,2
WScript.Echo objWSC.MyMethod2

Set objWSC=Nothing
WScript.Quit

Run the script, and the number "3" is echoed to the screen. Not overly impressive, but not bad for our first component!

Homework
To really demonstrate the flexibility of WSCs, your homework for this month is to take the "Customer" class I created in the July issue and turn it into a Windows Script Component. You may be surprised just how easy it is.

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