Adding Methods to Custom Class Objects in VBScript

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In my last article I began showing you how to create your own custom class objects in VBScript. We started building the CompressedFolder class, a class that allows you to create and manipulate compressed folders natively. This article will expand on what you learned.

We started by creating a class and adding various properties to it, but having a few properties doesn’t do much for this class.  We also need a way to create the compressed folder and to add to and remove files from it.  For that we need to add some methods.  These are the functions and subroutines that perform the magic when the class is called.

Just like Properties, these methods can be either Public or Private.  Again, the Public methods will be exposed to scripts through the class object.  The structure of methods is identical to that of functions and subroutines used outside of a class, with the simple exception that we’ll be providing either a private or public declaration.

   Public Sub Create(strFile)

       If objFso.FileExists(strFile) Then objFso.DeleteFile(strFile)

       FullName = strFile

       NewCompressedFolder FullName

   End Sub

 

   Private Sub NewCompressedFolder(strPath)

       Const adTypeBinary = 1

       Const adTypeText = 2

       Const adWriteChar = 0

       Const adSaveCreateNotExist = 1

       Const adSaveCreateOverwrite = 2

 

       With CreateObject("ADODB.Stream")

          .Open

          .Type = adTypeText

          .WriteText ChrB(&h50) & ChrB(&h4B) & ChrB(&h5) & ChrB(&h6)

          For i = 1 To 18

              .WriteText ChrB(&h0)

          Next

          .SaveToFile strPath, adSaveCreateNotExist

          .Close

          .Open

          .Type = adTypeBinary

          .LoadFromFile strPath

          .Position = 2

          arrBytes = .Read

          .Position = 0

          .SetEOS

          .Write arrBytes

          .SaveToFile strPath, adSaveCreateOverwrite

          .Close

       End With

   End Sub

Here I’ve added two methods to my class.  The Open() method is a Public method that can be used by the class object in my scripts.  When I pass a parameter to this method, the class will internally call the private NewCompressedFolder() method.

I could have easily housed all of the code in the NewCompressedFolder method within the Open method and eliminated the need for it.  I don’t like to do that.  I prefer to keep all of the internal workings of a class within its own private methods.  This is a pretty common practice for most programmers.

Next: Adding methods to a class >>
 

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