Microsoft WSH and VBScript Programming for the Absolute Beginner Part 39 pot

Function ProcessFirstHeroSet objFirstHero = New SuperHero ‘Instantiate a new SuperHero object objFirstHero.Name = “Captain Adventure” ‘Assign value to Name property objFirstHero.Power =

Function ProcessFirstHero()

Set objFirstHero = New SuperHero ‘Instantiate a new SuperHero object

objFirstHero.Name = “Captain Adventure” ‘Assign value to Name property objFirstHero.Power = “Laser Vision” ‘Assign value to Power property objFirstHero.Weakness = “Dog Whistle” ‘Assign value to Weakness property objFirstHero.Identity = “Bruce Tracy” ‘Assign value to Identity property

objFirstHero.DisplayIdentity() ‘Execute the SuperHero object’s method

End Function

Function ProcessSecondHero()

Set objSecondHero = New SuperHero

objSecondHero.Name = “Captain Marvelous” ‘Assign value to Name property objSecondHero.Power = “Lightning Speed” ‘Assign value to Power property objSecondHero.Weakness = “Blue Jello” ‘Assign value to Weakness property objSecondHero.Identity = “Rob Denton” ‘Assign value to Identity property

objsecondHero.DisplayIdentity() ‘Execute the SuperHero object’s method

End Function

Class SuperHero

Private strName, strPower, strWeakness, strIdentity ‘Define variables

‘used by this class

Public Property Let Name(strIdentity) ‘Define the Name property

strName = strIdentity

End property

Public Property Let Power(strSuperPower) ‘Define the Power property

strPower = strSuperPower

End property

Public Property Let Weakness(strHurtBy) ‘Define the Weakness property

strWeakness = strHurtBy

End property

Public Property Let Identity(strSecretIdentity) ‘Define the Identity

strIdentity = strSecretIdentity ‘property

End property

Function DisplayIdentity ‘This function defines the SuperHero object’s

‘DisplayIdentity() method MsgBox strName & vbCrLf & vbCrLf & _

“Hero Power: “ & vbTab & strPower & vbCrLf & _

“Hero Weakness: “ & vbTab & strWeakness & vbCrLf & _

“Hero Identity: “ & vbTab & strIdentity

End Function

Private Sub Class_Initialize ‘This event automatically executes when

‘the SuperHero object is instantiated MsgBox “In a blast of smoke and lightning another new super “ & _

“hero is born!”

End Sub

End Class

As the script runs, pop-up dialogs will be displayed as shown in Figures 11.8 and 11.9 demon-strating the execution of the Class_Initialize event and the object’s DisplayIdentity() method

Figure 11.8

The

Class_Initialize

event occurs

every time a new

instance of the

SuperHero object

is established.

Working with the Err Object

The Errobject provides access, via its properties, to information about run-time errors For example, using the Errobject’s Descriptionproperty you can retrieve a string containing an error’s description Using the Errobject’s Numberproperty you can retrieve the error number associated with an error and using the Err object’s Source property you can retrieve the name of the resource that reported the error

The Errobject also provides access to two methods The Clear()method clears out the prop-erties belonging to the Err object This is handy in situations where you can develop an effective error handling routine that enables your script to recover from an error and keep running The Raise() method is equally useful, giving you the capability to simulate run-time errors so that you can test out your script’s error handling procedures

For additional information and examples on how to work with the Errobject, refer to Chapter 9,

“Handling Script Errors.”

Working with Regular Expressions

All remaining VBScript built-in objects and collections deal with regular expressions A

regular expression is a pattern consisting of characters and metacharacters Regular expressions

are used as a means of searching and replacing patterns within strings

The first step in preparing your VBScripts to work with regular expressions is to instantiate the RegExpobject This object provides access to the remaining built-in VBScript objects The RegExpobject is instantiated as follows:

Dim objRegExp

Set objRegExp = New RegExp

Figure 11.9

The SuperHero

object’s Display

Identity()

method displays

the value of all

properties

assigned to an

instance of

an object.

The RegExp object provides access to the following properties:

• Pattern Identifies the pattern to be matched.

• IgnoreCase Contains a value of Trueor Falsedepending on whether a case-sensitive search is performed

• Global An optional Boolean value used to specify whether all occurrences of the

spec-ified pattern are to be replaced

The RegExp object provides access to several methods, including:

• Replace() Replaces matching string patterns

• Test() Performs a pattern search, generating a Boolean value based on whether a

match is found

• Execute() Provides the ability to generate a Matchescollection

Replacing Matching Patterns

Using the RegExpobject’s Replace()method, you can replace matching patterns within a string The syntax for this method is

RegExp.Replace(String1, String2)

String1 identifies the string to search and String2 identifies the replacement string To demonstrate how to work with the Replace()method, look at the following example: Dim objRegExp

Set objRegExp = New RegExp

objRegExp.Pattern = “planet”

MsgBox objRegExp.Replace(“A long time ago on a far away planet”, “world”)

In this example, a variable name objRegExpis defined, and then used to instantiate a refer-ence to the RegExpobject Next a value of planetis assigned to the RegExpobject’s Pattern property to define a search pattern Finally, the Replace() method is used to force the replacement of the word planetwith the word world Figure 11.10 shows the output gener-ated when this example is run

By default, the Replace()method only replaces the first occurrence of a match within the specified search string However, by setting the value of the RegExpobject’s Globalproperty

to Trueyou can force the replacement of all matching patterns To see this in action, mod-ify the previous example as follows

Dim objRegExp

Set objRegExp = New RegExp

objRegExp.Pattern = “planet”

objRegExp.Global = “True”

MsgBox objRegExp.Replace(“A long time ago on a far away planet”, “world”)

VBScript’s support for regular

expres-sions includes the capability to define

a host of complex pattern matches

through the use of metacharacters

Table 11.3 lists all the metacharacters

supported by VBScript

Figure 11.10

Using regular

expression

matching you

can substitute

a portion of

any string.

Definition

A metacharacter is a special character used to provide

information about other characters In the case of regu-lar expression, metacharacters specify how a matching pattern is to be processed.

Character Description

\ Sets the next character as a special character, a back reference, a literal, or an octal

escape

^ Matches the beginning of the input string

$ Matches the end of the input string

* Matches the preceding expression (zero or more times)

TA B L E 11 3 V B SC R I P T RE G U L A R EX P R E S S I O N ME TA C H A R A C T E R S

Character Description

+ Matches the preceding expression (one or more times)

? Matches the preceding expression (zero or one time)

{n} Matches exactly n times

{n,} Matches a minimum of n times

{n,m} Matches a minimum of n times and a maximum of m times

Matches any individual character except the newline character

(pattern) Matches a pattern and allows the matched substring to be retrieved from the

Matches collection.

x|y Matches x or y

[xyz] Matches any of the specified characters

[^xyz] Matches any character except those specified

[a-z] Matches character specified in the range

[^a-z] Matches character except for those specified in the range

\b Matches on a word boundary

\B Matches on a non-word boundary

\cx Matches the control character specified as x

\d Matches a single digit number

\D Matches any single non-numeric character

\f Matches the form-feed character

\n Matches the newline character

\r Matches the carriage return character

\s Matches any white space character (for example, space, tab, form-feed)

\S Matches any non-white-space character

\t Matches the tab character

\v Matches the vertical tab character

\w Matches any word character

\W Matches any non-word character

\xn Matches n, where n is a two-digit hexadecimal escape value

TA B L E 11 3 V B SC R I P T RE G U L A R

EX P R E S S I O N ME T A C H A R A C T E R S ( C O N T I N U E D )

(continues)

Character Description

\num Matches num, where num is a positive integer in a backward reference to captured

matches

\n Specifies an octal escape value or a back reference

\nml Matches octal escape value nml where n is an octal digit in the range of 0–3 and m

and l are octal digits in the range of 0–7

\un Matches n, where n is a four-digit hexadecimal Unicode character

TA B L E 11 3 V B SC R I P T RE G U L A R

EX P R E S S I O N ME T A C H A R A C T E R S ( C O N T I N U E D )

To better understand how to take advantage of metacharacters, take a look at the following example:

Dim objRegExp

Set objRegExp = New RegExp

objRegExp.Pattern = “[\d]”

objRegExp.Global = “True”

MsgBox objRegExp.Replace(“1 years ago on a far away planet”, “1000”)

In this example, specifying the \dmetacharacter as the value assigned to the RegExpobject’s Patternproperty results in a replacement operation where any single numeric character is identified as a match Figure 11.11 shows the output generated when you run this example

As you can see, in this example the number 1 is replaced by the number 1000

Testing for Matching Patterns

The RegExpobject’s Test()method performs a pattern match without actually performing a replacement operation The syntax for the Test()method is

RegExp.Test(string)

The following statements demonstrate how to use this method In this example, the script displays one of two messages, depending on whether the string assigned to the Pattern prop-erty is found within the search string

Dim objRegExp

Set objRegExp = New RegExp

objRegExp.Pattern = “planet”

If objRegExp.Test(“A long time ago on a far away planet”) = “True” Then

MsgBox “The word “ & objRegExp.Pattern & “ was found!”

Else

MsgBox “The word “ & objRegExp.Pattern & “ was not found!”

End If

Creating Matches Collections

Using the RegExpobject’s Execute()method, you can generate a Matchescollection as a result

of a regular expression search The syntax of the Execute()method is

RegExp.Execute(string)

Once generated, the Matchescollection is read-only It is made up of individual Matchobjects Each Matchobject has its own set of properties, which include:

• FirstIndex Retrieves the starting character positions of a match within a string

• Length Returns the length of a match found within a string

• Value Retrieves the text of the match found within a string

Once a Matchescollection has been generated, you can process all the members of the col-lection using a loop, as demonstrated by the next example

Dim objRegExp, objMatchCollection, objMatch, strStory, strDisplayMsg

Set objRegExp = New RegExp

Figure 11.11

Using

metacharacters

enables you to

perform complex

substitutions

objRegExp.Pattern = “bear”

objRegExp.Global = “True”

strStory = “Once upon a time there were three little bears There “ & _

“was mama bear, papa bear and baby bear There was cousin bear too!”

Set objMatchCollection = objRegExp.Execute(strStory)

For Each objMatch in objMatchCollection

strDisplayMsg = strDisplayMsg & “An instance of “ & _

objRegExp.Pattern & “ found at position “ & objMatch.FirstIndex & _

vbCrLf

Next

MsgBox strDisplayMsg

In this example, a For Each Nextloop was set up to process each Match object in the col-lection The Matchobject’s FirstIndexproperty was used to retrieve the starting position of each matching pattern in the search string, which was then used to generate the output shown in Figure 11.12

Back to the Tic-Tac-Toe Game

The heart of the Tic-Tac-Toe game lies in the design of its game board, which is divided into three sections Status and error messages are displayed at the top of the board to assist play-ers when mistakes are made playing the game

Figure 11.12

Using the RegExp

objects

Execute()

method to

generate and

process the

contents of a

Matches

collection.

In the middle of the board is an image of a traditional Tic-Tac-Toe board To the right and top of the Tic-Tac-Toe board are letters and numbers, the coordinates of each cell that make

up the game board Players play the game by using these letters and numbers to specify what cell they want to select as their next move Embedded within the board are variables representing each cell on the board The values assigned to these variables are set to either

an Xor Obased on the moves made by each player as the game progresses

The bottom of the game board is made up of an input text field that enables players to enter their moves In addition, instruction is provided just above this text field in the form of a text message that is used to keep track of player turns

Designing the Game

Besides its Initialization and Main Processing sections, the game is made up of nine func-tions Each function performs a specific task Here is a list of the script’s functions along with a brief description of their associated tasks:

• SetVariableDefaults().Establishes default values for various script variables

• ClearGameBoard().Resets each cell on the Tic-Tac-Toe game board so that it appears as blank or empty

• ManageGamePlay().Controls the overall execution of the game, calling on other func-tions as necessary

• DisplayBoard().Displays the game board along with instruction, error messages, and any moves already made by each player

• DisplayGameResults().Displays the final results of each game, identifying who won

or whether the game results in a tie

• ValidateInput().Ensures that players are only allowed to enter valid cell coordinates when taking their turns

• MarkPlayerSelection().Associates input provided by players with the appropriate cell coordinates on the game board

• SeeIfWon().Checks the game board to determine whether a player has won or

whether the game has ended in a tie

• DisplaySplashScreen().Displays information about the script and its author

Setting Up the Script’s Template and Initialization Section

The Tic-Tac-Toe game begins by defining the constants and variables used by the game Because the game uses a large number of variables, I embedded comments to the right of each variable to identify its purpose