Using a string's data as another var

[The_Inspector]

Hello Everyone,
I've been trying to find out if it's possible (and if it is how) to take the data in a String which is a name of another var, and save data to that other var...
Exampe:
Dim Temp as string
Dim AnotherVar as integer

Temp = "AnotherVar"
*** Lets say I want to save in AnotherVar the value "7", I don't want to write AnotherVar = 7, I want to find a way that I can do TheDataInTemp = 7
And since the Data in temp is the word "AnotherVar", it will save the value 7 in the AnotherVar variable that I defined at the begining...
Any Ideas?

[Yonatan]

You can't.
If we whine a lot, maybe it will be possible in VB7.

[The_Inspector]

Oh well,
Guess it's back to the ol' "case" command to do what I was thinking off...
Thanks Yonatan.
Btw: Any info about VB7's release date?

I believe what you want was called dynamic evaluation and was available in ALL the old database languages (DB, Revelation, clairion, RBase....), but these were all interpreted languages. Essentially, you put the command string into a string variable and invoked the execution function using the string as an argument.

At the time I studied compiliers (much longer ago than I wish to remember) there was a reason why this facility was not included. But I can't remember........

I have done something similiar involving tables and data, but it was kludgy and not worth the effort. If its really important, I could probably refine it.


Good Luck
DerFarm

[mlewis]

heh, once I had the same question and started writing code to handle that situation..I ended up with a scripting language and interpreter. Its a mess to try it...I say stick with Case and wait for VB7.

[Lyla]

Hi.

If i understand you correctly!
I had the same Q a while ago. Check this post :

http://forums.vb-world.net/showthrea...threadid=22984

Sascha's method did the trick.
I use it, and it's working.

Good Luck.

[PaulLewis]

If this is what you want. To take you literally, the other
var is already defined, so you are not really trying to
create new variables during runtime which I think a few of
the ohter replies assume.

To use the contents of a string to determine which of
several variables to change, is easiest to do with a big
case statement. Of course, I assume you do not want this
because perhaps you want to set/get this value from many
places in your code.

Although I cannot see any possible reason why you would
absolutely need this (there are always alternatives), I
have put together a simple piece of demo code which does
the following:

1) User selects a variable name from a combo
box (names hard coded in the list for the demo but you can
easily make the list dynamic)

2) User enters an integer value in the text box

3) User hits the command button, and the appropriate var is
updated . This is achieved without the use of any testing
of the user selection.

To use this in your code, you would have to do as I have
done and give VB an alternative way to address the var you
are after.

This method is only one such way to do this.

Option Explicit

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
    lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)

Dim AnotherVar As Integer
Dim AnotherVar2 As Integer
Dim sillyCol As Collection



Private Sub Command1_Click()
    Debug.Print AnotherVar, AnotherVar2
  
  ' set whichever var is selected form the combo box
  ' to the contents of the text box.
  On Error Resume Next
    Dim val As Integer
    val = CInt(Text1.Text)
    ' ignore conversion errors - leave as 0
    If Err <> 0 Then Err.Clear
    
    Dim myPointer As Long
    myPointer = CLng(sillyCol(Combo1.Text))
    If Err <> 0 Then
      MsgBox "the variable selected cannot be found in the collection"
      End
    End If
    
    CopyMemory ByVal myPointer, val, 2
    
    Debug.Print AnotherVar, AnotherVar2
  On Error GoTo 0

End Sub

Private Sub Form_Load()
  Set sillyCol = New Collection
  
  ' some test integers
  AnotherVar = -23
  AnotherVar2 = 1023
  
  ' record the varname against it's pointer
  sillyCol.Add Str(VarPtr(AnotherVar)), "AnotherVar"
  sillyCol.Add Str(VarPtr(AnotherVar2)), "AnotherVar2"
  
End Sub

Test it out for yourself.

Cheers

[ExcalibursZone]

>Dim Temp as string
>Dim AnotherVar as integer

>Temp = "AnotherVar"
>*** Lets say I want to save in AnotherVar the value "7", I
>don't want to write AnotherVar = 7, I want to find a way
>that I can do TheDataInTemp = 7
>And since the Data in temp is the word "AnotherVar", it
>will save the value 7 in the AnotherVar variable that I
>defined at the begining...
>Any Ideas?

Well, I stumbled across something ... it may not be the best
way to go about it, but it does indeed work.

Create a Class Called Class1;

'Setup as many of your variables here as you want. I chose 
'to use variants (I'm lazy ;>) Make sure you set them all
'up with properties as well (the name of your variable)
'I'm using your example.

Option Explicit

Private vAnotherVar As Variant

Public Property Let AnotherVar(tmpVar As Variant)
    vAnotherVar = tmpVar
End Property

Public Property Get AnotherVar() As Variant
    AnotherVar = vAnotherVar
End Property

On your form, add a nifty command botton called: Command1:

Option Explicit
Dim MyClass As New Class1
Dim Temp As String
Dim Data As String

Private Sub Command1_Click()
    Temp = InputBox("Enter a Variable Name (String)" & _
           vbCrLf & "No matter what's entered, it'll & _
           go to AnotherVar :)")
    Data = InputBox("Enter a String. Enter nothing to _
           clear the variable.")
    Temp = "AnotherVar"
    CallByName MyClass, Temp, VbLet, Data
    MsgBox CallByName(MyClass, Temp, VbGet)
End Sub

This is a nifty little Function/Statement if I do say so
myself. (made a lot of happy happies in my current project!)
What's happening is this: CallByName can be used as either a
function or as a Statement (Sub). It needs the following
parameters as follows:

variable = CallByName(object, method/property, method type, arguement1, arguement2, ..., argumentN)
CallByName object, method/property, method type, arguement1, arguement2, ..., arguementN

Object is a form, control, or object (hence myclass) Class
modules need to be declared before CallByName will work with
them and their methods/properties must be declared as
public.
Method/Property is the Function/Sub/Property you wish to
execute in the Object. That's where your variable name comes
into play. Set it up as a Property and you can call whatever
variable you want as long as the property name is the same
as the variable you wish to change during runtime with a
string.
Method Type is either vbGet, vbSet, vbLet, or vbMethod. Get
& Let are used with properties, get & set are used with
embedded objects, and method is used for functions & subs.

Arguement is an array which contains the data you wish to
pass to the property/method. You don't need the parens '()'
just seperate the arguments with commas.

So, there you have it. It's a round about way of doing it,
but it's the best thing that I found in VB that doesn't
require you to declare API stuff ;)