3rd ed./Ch.8/p.215-216: Something ain't right here...

arar · #1 (**permalink**) January 6th, 2009, 01:54 PM

Hello:

I was reading through Chapter 8 (3rd edition) and noticed a short comment that struck me as 'strange' (but not necessarily 'impossible').

Here the text segment that I think may not be correct (very last paragraph on p.215):

"The Set syntax inside of the Property Set and Let is optional. Because you write directly to the Variant private property variable, you can use either. ..."

To test this statement I entered the code shown on pages 215 (and again on 216). Below I pasted the code (if anyone wants to try it out). I ran said code with and without the Set inside of the Property segments (alternatively commented-out). I can't get this to run WITHOUT the Set statement and therefore I was wondering if anyone on here could shed some light on this situation (perhaps referencing the proper MSDN source at the same time)?

Most appreciated,

AR.

Inline Attachment:

Code:

Dim objFileHelper
Dim objFSO

Set objFSO = WScript.CreateObject("Scripting.FileSystemObject")
Set objFileHelper = New FileHelper

'with 'Set' (works only with 'Set' in class below):
Set objFileHelper.FSO = objFSO

'without 'Set' (again, works only with 'Set' in class below):
'objFileHelper.FSO = objFSO

Class FileHelper
'write-only class
    Private m_objFSO
    
    Public Property Set FSO(objFSO)
        'Set m_objFSO = objFSO
        m_objFSO = objFSO
    End property
    
    Public Property Let FSO(objFSO)
        'Set m_objFSO = objFSO
        m_objFSO = objFSO
    End Property
    
End Class

Old Pedant · #2 (**permalink**) January 7th, 2009, 12:53 AM

That comment just doesn't make sense.

The code *INSIDE* the Property subroutine is just ordinary VBScript code and isn't really "aware" at all that it IS inside of a Property Set. The VBScript compiler just generates byte code tokens pretty much on a one for one basis and then, when those tokens are interpreted, they are just sent through a massive SELECT CASE (actually, "switch" in the C++ code) that sends the interpreter off to do the right thing. And the code for "SET" or the [implied] LET is the same no matter where the byte code is encountered.

I strongly suspect that this comment may have been cloned from a book about VB6. Since that language *IS* truly compiled, it's quite possible that it might be able to supply the "missing" SET automatically. But of course it's equally possible that this is just a plain flat goof.

Need to download code?

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