Use a Variable to Retun an Element from a Type Array

I have several type structures that have many element names in common. Currently to deal with that I have a bunch of select cases to determine which type to use and then get the proper element. To avoid all the case statements it occurred to me I could use the replace function - but I can't get this to work. Here is a way dumbed down section of code to illustrate my requirement:

Type TEST
  lTest As Long
  iTest As Integer
  sTest As String
  'many more elements
End Type
Sub UseVaribleforType()
Dim T As TEST
Dim lRet As Long

T.lTest = 1
'this is where i would like to evaluate T.lTest with a variable
lRet = Evaluate(Replace("T.X", "X", "lTest"))

End Sub

What I would like to do is replace the "X" in "T.X" to get the T.lTest element. The above code gets a vartype error as my evaluate is returning a string. I tried to replace the quotes with another replace using chr(34) but that didn't work either.

SNB, I think this ones for you?

Thanks,

Thick fingered double post of the following.

I see a User Defined Type called Test, that has 3 elements (lTest, iTest, and sTest).

It looks like the question you want answered is "given a variable V of type Test, and a value x, which element of V has a value of X"?

Your Select Case construct is probably the best way to approach this.

Mike,
Thanks for the quick response. I have 5 different types and they have at least 20 elements in common. This forces me to do the 5 case select case construct 20 times! It works but it is ugly, if I could find a way to get to the type via a variable I would only have to do the case once. I suspect I don't have a choice but I had to ask. I have seen SNB do some really wild stuff with replace so hopefully he will take a gander at this post.

Regards,

You could use a class instead of a user defined type, then you could use CallByName.

Class Module : TEST

Option Explicit


Dim plTest As Long
Dim piTest As Integer
Dim psTest As String

Property Get iTest() As Integer
    iTest = piTest
End Property

Property Let iTest(Value As Integer)
    piTest = Value
End Property

Property Get lTest() As Long
    lTest = plTest
End Property

Property Let lTest(Value As Long)
    plTest = Value
End Property

Property Get sTest() As String
    sTest = psTest
End Property

Property Let sTest(Value As String)
    psTest = Value
End Property

Standard Module

Sub UseVaribleforType()
Dim T As TEST
Dim lRet As Long

    Set T = New TEST

    T.lTest = 1
    'this is where i would like to evaluate T.lTest with a variable
    lRet = CallByName(T, "lTest", VbGet)
    MsgBox lRet

End Sub

Norie,
That's a great solution. However, the actual UDTs are from WINAPI and it won't accept classes in lieu of UDTs.

Thanks,

There is no equivalent for UDTs that I know of - Evaluate will not work here.

Can you give a specific example of why you need this, and how you are coding it now? Would it help to put the common fields into a new UDT and have that as a member of each relevant UDT?

Rory,
It's really a long story (and several hundred lines of code) but I am trying to set a dozen or so extended printer settings (like NUP) which requires manipulating DEVMODE types. In my code there are 5 different DEVMODES based on Universal vs. PostScript and also Windows versions. Snippet of the code (reduced DEVMODES to 3 and features to 3 for ease of viewing) looks like this:

Option Base 1
Option Explicit

Private Type DEVMODE_A
  'many more elements
  dmOrientation As Integer
  dmPaperSize As Integer
  'many more elements
  dmFormName As String * 32
  'many more elements
End Type
Private Type DEVMODE_B
  'many more elements
  dmOrientation As Integer
  dmPaperSize As Integer
  'many more elements
  dmFormName As String * 32
  'many more elements
End Type
Private Type DEVMODE_C
  'many more elements
  dmOrientation As Integer
  dmPaperSize As Integer
  'many more elements
  dmFormName As String * 32
  'many more elements
End Type
Type TT
  lTest As Long
End Type
Sub SetDevModebyType(Feature As Long, Setting As Variant)
Dim DMType As Long
Dim DEVMODE_A As DEVMODE_A
Dim DEVMODE_B As DEVMODE_B
Dim DEVMODE_C As DEVMODE_C
Dim lRet As Long

DMType = GetDevmodeType 'Returns 1,2 or 3

'Fill the correct DEVMODE based on DMType
Select Case DMType
  Case 1
    DEVMODE_A = GetDevModeA
  Case 2
    DEVMODE_B = GetDevModeB
  Case 3
    DEVMODE_C = GetDevModeC
 End Select

'Apply the setting for the Feature in the right DEVMODE

Select Case Feature
Case DM_ORIENTATION
  Select Case DMType
    Case 1
      DEVMODE_A.dmOrientation = Setting
    Case 2
      DEVMODE_B.dmOrientation = Setting
    Case 3
      DEVMODE_C.dmOrientation = Setting
  End Select
Case DM_PAPERSIZE
  Select Case DMType
    Case 1
      DEVMODE_A.dmPaperSize = Setting
    Case 2
      DEVMODE_B.dmPaperSize = Setting
    Case 3
      DEVMODE_C.dmPaperSize = Setting
  End Select
Case DM_FORMNAME
  Select Case DMType
    Case 1
      DEVMODE_A.dmFormName = Setting
    Case 2
      DEVMODE_B.dmFormName = Setting
    Case 3
      DEVMODE_C.dmFormName = Setting
  End Select
End Select

Select Case DMType
  Case 1
    Call CopyMemory(yDevModeArr(1), DEVMODE_A, Len(DEVMODE_A))
  Case 2
    Call CopyMemory(yDevModeArr(1), DEVMODE_B, Len(DEVMODE_B))
  Case 3
    Call CopyMemory(yDevModeArr(1), DEVMODE_C, Len(DEVMODE_C))
End Select

End Sub

While this method works, what I am trying to avoid are the interior cases which have to be repeated for each feature. I was hoping there was a way (such as evaluate and replace) to replace each of these cases with a single line that would set the feature to the correct DEVMODE.

I had previously tried your type within a type method but that doesn't help with this particular issue.

Note: I played around with conditional compiling but that won't work as I don't know the printer driver type (and thus DEVMODE type) until well into program execution.

Thanks,

The best I can think of at the moment is to use classes as Norie suggested, which at least removes a lot of the Select Case coding. For example:

Class DM_A:

Option Explicit

Private dma As DEVMODE_A

Public Property Let dmOrientation(ByVal value As Integer)
    dma.dmOrientation = value
End Property
Public Property Let dmPaperSize(ByVal value As Integer)
  dma.dmPaperSize = value
End Property
'many more elements
Public Property Let dmFormName(ByVal value As String)
  dma.dmFormName = value
End Property

Public Property Get DEVMODE() As DEVMODE_A
    DEVMODE = dma
End Property
Public Property Let DEVMODE(value As DEVMODE_A)
    dma = value
End Property

The other DEVMODEs would need similar classes.

Then your routine becomes something like:

Sub SetDevModebyType(Feature As String, Setting As Variant)
    Dim DMType As Long
    Dim DEVMODE_A As DEVMODE_A
    Dim DEVMODE_B As DEVMODE_B
    Dim DEVMODE_C As DEVMODE_C
    Dim oDevModeA As DM_A
    Dim oDevModeB As DM_B
    Dim oDevModeC As DM_C
    Dim lRet As Long
    
    DMType = getDevModeType 'Returns 1,2 or 3
    
    'Fill the correct DEVMODE based on DMType
    Select Case DMType
      Case 1
        Set oDevModeA = New DM_A
        DEVMODE_A = GetDevModeA
       oDevModeA.DEVMODE = DEVMODE_A
        'Apply the setting for the Feature in the right DEVMODE
        CallByName oDevModeA, Feature, VbLet, Setting
            Call CopyMemory(yDevModeArr(1), oDevModeA.DEVMODE, Len(oDevModeA.DEVMODE))
      Case 2
        Set oDevModeB = New DM_B
        DEVMODE_B = GetDevModeB
       oDevModeB.DEVMODE = DEVMODE_B
        CallByName oDevModeB, Feature, VbLet, Setting
            Call CopyMemory(yDevModeArr(1), oDevModeB.DEVMODE, Len(oDevModeB.DEVMODE))
      Case 3
        Set oDevModeC = New DM_C
        DEVMODE_C = GetDevModeC
       oDevModeC.DEVMODE = DEVMODE_C
        CallByName oDevModeC, Feature, VbLet, Setting
            Call CopyMemory(yDevModeArr(1), oDevModeC.DEVMODE, Len(oDevModeC.DEVMODE))
     End Select
        
End Sub

Where you now pass the feature as a string:

Sub foo()
    SetDevModebyType "dmOrientation", 5
End Sub

Would that help at all?

Note: you could probably also just have one class with all the possible properties and 5 separate properties for accessing each of the relevant DEVMODE types within the class.