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CONSTANTS LET US WRITE CLEARER CODE by replacing raw numbers and text strings with meaningful names. For numbers, there are at least three ways to do this in VB: the `Const´ statement, enumerated types
and read-only properties. Whichever way we choose, constants help us to write programs that are easier to read, and hence easier to understand. The uses of constants may be blindingly obvious, but some people just
don´t get it. I´ve seen a number of bewildered programmers define constants called `ZERO´, but the programmer whose code appears here here displays even more confusion. First he unwisely uses the same `vb´ prefix as
constants in the VBA library, and then he attempts to distinguish his constants from the VBA ones by adding his name to the prefix. But there´s worse to come. With the prefixes in hand (or out of hand,
depending on how you look at it), our programmer then goes on to choose completely token names for his constants before inexplicably commenting each use of a constant with the actual value. This code bears all the signs
of adhering to the letter of a coding standard without evidence of the slightest comprehension.
Constants From Hell
This code was written by an `experienced´ VB contract programmer who was probably earning
in the region of £40 per hour. I haven´t modified it in any way except to change the programmer´s name to `dave´. This guy has more to worry about than his constant names...
Sub ProcessInputValidate(Optional ByVal nKeyAscii As Integer)
Dim nCheckIt As Integer, sMsg As String
Const davevbMinusOne As Integer = -1
Const davevbZero As Integer = 0
Const davevbOne As Integer = 1
Const davevbTwo As Integer = 2
Const davevbThree As Integer = 3
Const davevbFour As Integer = 4
'initialise this
nCheckIt = davevbMinusOne '-1
If Len(Trim$(txtOrderNo)) = 0 Then
nCheckIt = davevbFour '4
sMsg = "Please enter the Item Number"
GoSub CheckValidation
ElseIf Len(txtOrderNo) < 8 Then
nCheckIt = davevbFour '4
sMsg = "Item Number should be 8-digits in length"
GoSub CheckValidation
End If
'Do a bit of Validation here
If Not VerifyRequiredField(txtInput(0)) Then
nCheckIt = davevbZero '0
sMsg = "Please enter Department Code "
ElseIf Not VerifyRequiredField(txtInput(1)) Then
nCheckIt = davevbOne '1
sMsg = "Please enter Product Code "
ElseIf Not VerifyRequiredField(txtInput(2)) Then
nCheckIt = davevbTwo '2
sMsg = "Unit Size needs to be entered"
ElseIf Not VerifyRequiredField(txtInput(3)) Then
If Not IsNumeric(txtInput(3)) And Len(Trim$(txtInput(3))) <> 0 Then
sMsg = "Please enter only numbers in this box"
nCheckIt = davevbThree '3
ElseIf Len(Trim$(txtInput(3))) = 0 Then
sMsg = "Please enter Number of Unit(s) required"
nCheckIt = davevbThree '3
Else
txtInput(3) = txtInput(3)
End If
End If
CheckValidation:
If Not (nCheckIt = davevbMinusOne) Then '-1
MsgBox sMsg, vbInformation, "Data entry Error"
If nCheckIt = davevbFour Then '4
txtOrderNo.SetFocus
Else
txtInput(nCheckIt).SetFocus
End If
GoSub Sub_Exit
End If
'When it reaches here all validation accepted
If cmdAddToColn.Caption = "&Amend Detail" Then
'We are going to Amend Details
AddAndRefresh ("AMENDTC")
Else
'We are going to Add details, this actually uses the
default values
Call AddAndRefresh
End If
'This will be maintaining the Amend/Update button, setting it to the default
If cmdAddToColn.ForeColor = davevbBlue Or cmdAddToColn.Caption = "&Amend Detail" Then
cmdAddToColn.ForeColor = vbBlack:
cmdAddToColn.Caption = "&Add Detail"
cmdAmend.Enabled = True
End If
Sub_Exit:
Exit Sub
Sub_Exit_Err:
End Sub |
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