Learn To Program Objects With Visual Basic 6

Muska and Lipman

1929-685-165

Errata and FAQ's
(Last Update: May 17, 2006)

Errata list

General #1---Unexpected Error--call John Smiley

At any rate, the program can only run from this location

            C:\VBFILES\CHINA

so make sure you copy the files there. Any other location will cause this problem. And after you copy the files, make sure they are NOT marked Read-only--something that happens when you copy from a CD.

General #2---Copied Files are read only

Not an errata, but ...

If you copy the sample files from the enclosed CD-ROM to your hard drive, most likely they will be marked read-only.

When you try to access the China Database, you'll receive an error message that reads

The Microsoft Jet database engine cannot open the file "C:\VBFiles\China\China.mdb".
It is already opened exclusively by another user, or you need permission to view its data."

To fix this, all you need to do is open up the Windows Explorer, select the China Shop Database, then right click your mouse to bring up the Properties Window. Un-check the read-only attribute, and you should be fine.

General #3---Word 2000

Not an errata but..

I recently received this email from a reader---many thanks, as he answered a question that has been troubling several readers

Professor Smiley, I ran into a problem while working through your Learn to Program Objects with Visual Basic 6 book.  It has to do with creating Word applications.  I used about every variation imaginable to create the Word.Application object.  Everything I tried resulted in the same error message, "Error: 429, ActiveX component can't create object".   I should mention that I'm running Office 2000 on a Windows 2000 machine.  I spent days trying to figure out what was wrong.  I tried re-installing Word, replacing MSWORD9.OLB (the Microsoft Word 9.0 Object Library file), downloading an Office Registry Repair utility from Microsoft (which interestingly, worked twice before giving me the error message), everything I could think of.  Then I ran across someone else who had encountered a similar problem in one of the newsgroups.  As it turns out, the problem occurs when you also have Norton Anti-Virus running.  I had to unregister NAV (regsvr32 /u "c:\program files\navnt\officeav.dll"), then everything worked fine.  What a relief!   I just thought I'd pass this along in case you get any inquiries from students experiencing similar problems.  

General #4--Error Handler in original code

There's a bug in the Error Handler for the load procedure of the main form.

If the PRICES.TXT file is not found, we detect it properly, but we wind up generating a cascading form load event. To correct that, you need to follow these steps in the Load Event Procedure of the Main form.

After executing the line of code reading 'Unload frmMain' we should also execute the 'End' statement. Like this:

Unload frmMain
End
Exit Sub

Chapter 1

None that we know of

Chapter 2

• Page 143, Step 2, screenshot. It doesn't really matter, but there is a space after "Corelle" and the number 4, and after "Faberware" and the number 10.
• Page 147, first new line of code. strBrand is declared, assigned the selected item in the textbox, but then never used again.

  The code was going in the right direction--- assigning the text property to a variable and using the value of the variable in the comparison expression for each of the If statements is more efficient code-- as each 'read' of a property requires two Input-Output operations. Looks like I started to do that, and didn't follow through.

Chapter 3

• Page 178, steps 2 and 3. If App.Path = "\" should be If Len(App.Path) = 3. The Len function returns the length of a string, and the length of the Path property will ONLY be 3 if the path is the root directory.
• Page 183. The list of "vbCF..." constants does not contain the "vbCFRTF" constant for Rich Text that is used in the example on page 184. It is also not listed in the "GetFormat" section of the MSDN Library, though it appears in the "Clipboard Object Constants" section. vbCFRTF, according to the Object Browser, has a value of 16,639. Because of that, the code on Page 184 is incorrect. 
• Page 210. Last line - "clicked on the form." should be "clicked on the command button."
• Page 217, In the table, "VBIconPointe" should be "VBIconPointer".

Chapter 4

• Page 250, screen shot. Caption on first (backmost) form should be "Form1"
• Page 256 Paragraph 3, last sentence. "When it sees ...increment the value by 1." Delete this sentence. Check1(1) refers to that specific control.
• Page 257, Paragraph 3, 3rd line from the end. "Left" should be "Top"

Chapter 5

• Page 305, 3rd line. txtPaper should be txtTermpaper.
• Page 338. The comment on Page 305 about m_sngAverage is ironic, since eagle eyed readers (thanks Jim Richards!) point out that the student's class average isn't being written to our output file. For that matter, the overall class average is not being computed properly either. The problem is that when me make our changes to the Student project in this chapter, we allow the Student class to calculate the student's average, and we never set the value of m_sngAverage to this value. For that reason, add this line of code right before the line of code that sets stuNew to Nothing.

       m_sngFinalGrade = stuNew.Average

• Page 354, shaded new code area, Line 2. "Dim strTest As String" may be deleted. It is not referred to in the program.
• Page 354, 368. All occurrences of "If App.Path = "\" Then" should be changed to

If Len(App.Path) = "3" Then

Page 355, the Error Handler. Add

End

after 

Unload frmMain

• Page 372, last line. "Exit Sub" should be shaded as a new line.
• Page 373, the Error handler should be

    MsgBox Err.Number & ": " & Err.Description

• Page 374. One of my readers, Scott Leonard,, points out that we could use a test for 'Is Nothing' instead of trapping for Error 91. I had this coded up in the original draft of my book, but was wary of including it because Microsoft indicated it doesn't always work---however, I've never known it to fail, so I'm including Scott's alternate code here for you.

' Check to see if any of the Dish types are instantiated...my change to the code on pg 374

If Not m_dshPlate Is Nothing Then
    curPlatePrice = m_dshPlate.Price
Else
    curPlatePrice = 0
End If

If Not m_dshButterPlate Is Nothing Then
    curButterPlatePrice = m_dshButterPlate.Price
Else
    curButterPlatePrice = 0
End If

If Not m_dshSoupBowl Is Nothing Then
    curSoupBowlPrice = m_dshSoupBowl.Price
Else
    curSoupBowlPrice = 0
End If

If Not m_dshCup Is Nothing Then
    curCupPrice = m_dshCup.Price
Else
    curCupPrice = 0
End If

If Not m_dshSaucer Is Nothing Then
    curSaucerPrice = m_dshSaucer.Price
Else
    curSaucerPrice = 0
End If

If Not m_dshPlatter Is Nothing Then
    curPlatterPrice = m_dshPlatter.Price
Else
    curPlatterPrice = 0
End If

• Page 385, 3 lines from the bottom. "Shorly, we'll be remove all.." should be "Shortly, we'll be removing all..."

Chapter 6

• General. From this point forward, change the data type of the variable m_intRunningTotal to a Single instead of an Integer (thanks Jim Richards!)
• Page 419. All occurrences of "If App.Path = "\" Then" should be changed to

  If Len(App.Path) = "3" Then

• Page 420, the Error Handler. Change both instances of the Unload statement to  

        Unload frmShipping

Chapter 7

• Page 484, under Discussion. There's a mention of using the Count property in the Click event procedure of cmdClassAverage. Actually, at this point we're dealing with the China Shop project---and we'll use the Count property of the Colleciton object in the TotalPrice Method we code on page 486.
• Page 498, Exercise, Step 2. This code, as written, has a very subtle bug. If, after placing a legitimate order, if you click on the Reset button, then select an item BEFORE selecting a brand, then click on a brand, the program will attempt to remove a non-existing item from the collection. Add this line of code right before the End Sub

  m_strOldBrand = ""

  and move the End Sub to a new line.

Chapter 8

• Page 548. The second Alert Box says: "We've included a text file that contains the exact text of this macro in the download. You can find it in the For Chapter 08\ etc. etc.". It's actually in the folder "For Chapter 09\ etc. etc.. Agree? Jim.
• Page 549. A reader with Word 2000 reports that the line of code reading

  .Selection.TypeText Text:="Class Average" & vbTab & vbTab & _
  vbTab & vbTab & m_objCourse.ClassAverage

  would not work until she changed it to

  .Selection.TypeText Text:="Class Average" & vbTab & vbTab & _
  vbTab & vbTab & "Str(m_objCourse.ClassAverage)"

• Page 567. There's a VB bug which causes the code in cmdPrint to bomb the second time the print button is clicked. Add this code to the end of the procedure.

  Set Word.Global = Nothing
  

Chapter 9

• Page 615. All occurrences of "If App.Path = "\" Then" should be changed to

If Len(App.Path) = "3" Then

• Page 626. The code at the top of the page should be:
  
  For intCounter = 4 to 54 
  
  Not 5 to 54
  
  

Chapter 10

• Page 634. Quotation marks have been left off the PathName and FileName entires--and the slashes shown should be backslashes. Therefore, this

        regsvr32 c:/vbfiles/practice/activexdll/academicssupport.dll /u

        should be

        regsvr32 "c:\vbfiles\practice\activexdll\academicssupport.dll" /u

• Page 635. Screenshot is wrong---per the above.

• Page 636. Quotation marks have been left off the PathName and FileName entires--and the slashes shown should be backslashes--as above.

• Page 637. Screenshot is wrong---per the above.

• Page 638. Quotation marks have been left off the PathName and FileName entires--and the slashes shown should be backslashes--as above. 

  Therefore, this

   

          regsvr32 c:/vbfiles/practice/activexdll/academicssupport.exe /u

   

          should be

   

          regsvr32 "c:\vbfiles\practice\activexdll\academicssupport.exe" /u

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