Microsoft WSH and VBScript Programming for the Absolute Beginner Part 23 potx

Specifically, you will learn how to • Create your own customized functions • Create reusable collections of statements using subroutines • Break down scripts into modules of code to make

Set objNewShortcut = objWshShl.CreateShortcut(strAppDataPath + _

“\\GuessANumber.lnk”)

objNewShortcut.TargetPath = “C:\ GuessANumber.vbs”

objNewShortcut.Save

What makes working with the Quick Launch toolbar different than working with other Windows special folders is that you must specify the location of the Quick Launch toolbar within the special folder (AppData) that contains it

Figure 6.17 shows how the Quick Launch toolbar appears once the shortcut of your VBScript game has been added to it

A Complete Shortcut Script

Now let’s put together some of the shortcut examples you worked on previously to make a new script that creates shortcuts for GuessANumber.vbson the Windows desktop, Programs menu, and Quick Launch toolbar

‘*************************************************************************

‘Script Name: ShortcutMaker.vbs

‘Author: Jerry Ford

‘Created: 11/28/02

‘Description: This script creates shortcuts for the GuessANumber.vbs

‘VBScript ‘on the Windows desktop, Programs menu, & Quick Launch Toolbar.

‘*************************************************************************

‘Initialization Section

Option Explicit

Dim objWshShl, strTargetFolder, objDesktopShortcut, objProgramsShortcut

Dim strAppDataPath, objQuickLaunchShortcut

Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition

Figure 6.17

Examining the

Windows Quick

Launch toolbar

after adding a

shortcut to

the GuessA

Number.vbs

game.

Guess a Number

‘Establish an instance of the WshShell object

Set objWshShl = WScript.CreateObject(“WScript.Shell”)

‘Create the Desktop shortcut

strTargetFolder = objWshShl.SpecialFolders(“Desktop”)

Set objDesktopShortcut = objWshShl.CreateShortcut(strTargetFolder +

“\\GuessANumber.lnk”)

objDesktopShortcut.TargetPath = “C:\ GuessANumber.vbs”

objDesktopShortcut.Description = “Guess a Number Game”

objDesktopShortcut.Hotkey = “CTRL+Alt+G”

objDesktopShortcut.Save

‘Create the Programs menu shortcut

strTargetFolder = objWshShl.SpecialFolders(“Programs”)

Set objProgramsShortcut = objWshShl.CreateShortcut(strTargetFolder &

“\\GuessANumber.lnk”)

objProgramsShortcut.TargetPath = “c:\ GuessANumber.vbs”

objProgramsShortcut.Save

‘Create the Quick Launch Toolbar shortcut

strTargetFolder = objWshShl.SpecialFolders(“AppData”)

strAppDataPath = strTargetFolder + “\Microsoft\Internet Explorer\Quick Launch”

Set objQuickLaunchShortcut = objWshShl.CreateShortcut(strAppDataPath +

“\\GuessANumber.lnk”)

objQuickLaunchShortcut.TargetPath = “C:\ GuessANumber.vbs”

objQuickLaunchShortcut.Save

I achieved a few economies of scale here First of all, I only had to instantiate the WshShell object once I also reused the strTargetFolder variable over and over again However, I thought that it made the script more readable to assign a different variable to each special folder reference Run this script and you should see shortcuts for GuessANumber.vbsadded to the Windows desktop, Programs Menu, and Quick Launch toolbar

Summary

In this chapter you learned about loops and how to apply them to your VBScripts You demonstrated your understanding of this fundamental programming concept through the development of the Guess a Number game You also leaned how to programmatically work with Windows shortcuts, and how to use them to create shortcuts for your scripts, as well

as how to configure a number of Windows features, including the Windows desktop, Start Menu, and Quick Launch toolbar

202 Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition

CH A L L E N G E S

1 Modify the Guess a Number Game by providing the players with better hints For example, if a user’s guess is within 20 numbers of the answer, tell the player that

he is getting warm As the player gets even closer to the correct guess, tell him that he is getting very hot.

2 Change the Guess a Number game to increase the range of numbers from 1 to

100 to 1 to 1000.

3 Rewrite the Pick a Number Game so it uses a Do While statement in place of a

Do Until statement.

4 Use ShortcutMaker.vbs as a starting point, and write a new script that creates one

or more shortcuts for your favorite VBScript game Alternatively, if you keep all your VBScripts in one location, create a shortcut to that folder.

Using Procedures

to Organize

Scripts

7

By now you’ve seen and worked on a number of VBScript projects in this

book, and all of these scripts have been organized the same way First, you’ve set up script initialization processes (defining variables, constants, objects, and so on), and then you sequentially wrote the rest of the script as one big collection of statements You’ve then used the Ifand Select Casestatements

to organize your scripts Finally, by embedding statements within one another you have further refined your scripts’ organization In this chapter, you will learn how to further improve the organization of your VBScripts, using procedures Specifically, you will learn how to

• Create your own customized functions

• Create reusable collections of statements using subroutines

• Break down scripts into modules of code to make them easier to manage

• Control variable scope within your scripts using procedures

Project Preview: The BlackJack Lite Game

In this chapter, you create a game called BlackJack Lite This game is based on the classic blackjack game played in casinos around the world In this game, both the player and the computer are dealt a single card, face up The object of the game

is to try to get as close as possible to a value of 21 without going over The player can ask for as many extra cards (hits) as desired and can stop (stick) at any time

If the player goes over 21, he or she busts Otherwise the computer plays its hand, stopping only after either reaching a total of 17 or more or busting Figures 7.1 through 7.5 demon-strate the game in action

Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition

Figure 7.1

The game’s splash

screen invites

the user to play

a game of

BlackJack Lite.

Figure 7.2

If the user

declines, the

game displays

information about

itself and its

author and invites

the user to play

later.

Figure 7.3

If the user

accepts the offer

to play, the initial

hands are dealt.

By the time you’ve worked your way through this chapter and completed the BlackJack Lite game, you will have gained a solid understanding of how to use procedures You will be able

to improve the overall organization and functionality of your VBScripts and tackle even more challenging projects

Improving Script Design with Procedures

VBScript procedures improve the overall organization

and readability of scripts giving you a way to group

related statements and execute them as a unit Once

written, a VBScript procedure can be called on from

any location in your script and can be executed over

and over again as needed This enables you to create

scripts that are smaller and easier to maintain

VBScript provides support for two different types of procedures

• Sub A VBScript procedure that executes a set of statements without returning a result

• Function A VBScript procedure that executes a set of statements and, optionally, returns a result to the statement that called it

Figure 7.4

The user plays

until either

busting or

holding.

Figure 7.5

The computer

then plays and

the results of the

game are shown.

Definition

A procedure is simply a collection

of VBScript statements that, when called, are executed as a unit.

I recommend using procedures as the primary organization tool for all VBScripts

By organizing a script into procedures, you break it down into a collection of units This allows you to separate processes from one another, making it easier to develop scripts in a modular fashion, one component at a time

Introducing Subroutines

The VBScript Subprocedure is used to create subroutines Subroutines are great for group-ing together statements that perform a common task from which a result is not required When called, subroutines execute their statements and then return processing control back

to the calling statement

The syntax for this type of procedure is as follows:

[Public | Private] Sub name [(arglist)]

statements

End Sub

Privateis an optional keyword that specifies the subroutine cannot be called by other pro-cedures within the script, thus limiting the ability to reference it Publicis an optional key-word that specifies the subroutine can be called by other procedures within the script name

is the name assigned to the subroutine Like variables, a subroutine’s name must be unique within the script that defines it arglistrepresents a list of one or more comma-separated arguments that can be passed to the subroutine for processing, and statementsrepresents the statements that make up the subroutine

For example, the next subroutine is called DisplaySplashScreen() It does not accept any arguments and it does not return anything back to the VBScript statement that calls it What it does is display a script’s splash screen any time it is called

Sub DisplaySplashScreen()

MsgBox “Thank you for playing the game © Jerry Ford 2002.” & _

vbCrLf & vbCrLf & “Please play again soon!”, 4144, “Test Game”

End Sub

You can execute this subroutine by calling it from anywhere within your script using the fol-lowing statement:

DisplaySplashScreen()

The following example is a rewrite of the previous subroutine; only this time the subroutine has been rewritten to accept an argument The argument passed to the subroutine will be a

T R I C K

Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition

message Using a subroutine in this manner, you can develop scripts that display all their pop-up dialogs using one subroutine

Sub DisplaySplashScreen(strMessage)

MsgBox strMessage, 4144, “Test Game”

End Sub

You can call this subroutine from anywhere within your script like this:

DisplaySplashScreen(“Thank you for playing the game © Jerry Ford “ &_

“2002.” & vbCrLf & vbCrLf & “Please play again soon!”)

Creating Custom Functions

Functions are almost exactly like subroutines Functions can do anything that a subroutine can do In addition, a function can return a result back to the statement that called it As a result (to keep things simple), I usually use functions only within my VBScripts

The syntax for a function is as follows:

[Public | Private] Function name [(arglist)]

statements

End Function

Private is an optional keyword that specifies that the function cannot be called by other procedures within the script, thus limiting the ability to reference it Publicis an optional keyword that specifies that the function can be called by other procedures within the script nameis the name assigned to the function Like variables, a function’s name must be unique within the script that defines it arglistrepresents a list of one or more comma-separated arguments that can be passed to the function for processing, and statementsrepresents the statements that make up the function

Let’s look at an example of a function that does not return a result to its calling statement Function DisplaySplashScreen()

MsgBox “Thank you for playing the game © Jerry Ford 2002.” & _

vbCrLf & vbCrLf & “Please play again soon!”, 4144, “Test Game”

End Function

As written, this function performs the exact same operation as the subroutine you saw previ-ously This function can be called from anywhere in your script using the following statement: DisplaySplashScreen()

As with subroutines, you may pass any number of arguments to your functions, as long as commas separate the arguments, like this:

Function DisplaySplashScreen(strMessage)

MsgBox strMessage, 4144, “Test Game”

End Function

Once again, this function is no different from the corresponding subroutine example you just saw, and can be called as follows:

DisplaySplashScreen(“Thank you for playing the game © Jerry Ford “ &_

“2002.” & vbCrLf & vbCrLf & “Please play again soon

Functions also can be set up to return a result to their calling statement This is achieved by creating a variable within the function that has the same name as the function, and by set-ting the variable equal to the result that you want the function to return

Again, this technique can best be demonstrated with an example

strPlayersName = GetPlayersName()

MsgBox “Greetings “ & strPlayersName

Function GetPlayersName()

GetPlayersName = InputBox(“What is your first name?”)

End Function

The first statement calls a function name GetPlayersName() The second statement displays the results returned by the function and stored in the variable called PlayersName The next three lines are the actual function, which consists of a single statement that collects the player’s name and assigns it to a variable named GetPlayersNameso that it can be passed back

to the calling statement

Another way to call a function is to reference it as part of another VBScript statement, like this:

MsgBox “Greeting “ & GetPlayersName()

Improving Script Manageability

As I said before, by organizing your VBScripts into procedures, you make them more man-ageable, allowing you to create larger and more complex scripts without adding mounds of complexity As an example, let’s say that you’re developing a game that performs the five major activities that follow:

Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition

• Initializes variables, constants, and objects used by the script

• Asks the player whether he or she wants to play the game

• Collects the player’s name

• Displays a story, substituting the player’s name at predetermined locations within the story

• Displays a closing dialog inviting the player to play again on another day

One way to design your script would be to first define the variables, constants, and object references, and then create a series of functions and subroutine calls from the script’s main processing section The rest of the script would then consist of individual functions and sub-routines, each of which would be designed to perform one of the activities outlined in the previous list

Writing Reusable Code

One of the biggest advantages provided by functions and subroutines is the capability to create reusable code within your VBScripts Any time you find yourself needing to perform the same task over and over in a script—such as displaying messages in popup dialogs or retrieving random numbers—consider creating a function or subroutine Then, by using a single statement to call the appropriate procedure, you can reuse the statements located within the procedure over and over again

Functions and subroutines help make for smaller scripts They also make script mainte-nance and enhancement much easier and quicker For example, it’s a lot easier to change one line of code located in a procedure than it is to make that same change in numerous places throughout a script

In the Real World

One sign of a world-class programmer is the path that he or she leaves behind—in other words, the professional way in which the programmer organizes and documents his or her scripts One organizational technique used by experienced programmers is to group all functions and subroutines together in one place, apart from the initialization and main processing sections

of the script This makes them easy to locate and maintain Usually, you’ll find a script’s func-tions and subroutines located at the bottom of the script I suggest that you modify your script template to include a Procedure section for this purpose.