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Pass Array of doubles(using Delphi Dll)  to VB??

Posted on 2002-04-25
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Last Modified: 2008-02-01
Hi All,

I built a win32 dll in delphi, then I want to use this
in my VB:
Delphi Dll code:
Function SumArray(ar : OleVariant): double;stdcall;
var r : double; i, h, l : integer;
begin
    try
        if TVarData(ar).VType=varArray then
        begin
            h := VarArrayHighBound(ar,1);
            l := VarArrayLowBound(ar,1);
            r := 0;
            for i := l to h do
            begin
                 r := r + ar[i];
            end;
            result := r;
        end
        else
            result := -1;
    except
        result := -1;
    end;
end;
Exports
    SumArray;
begin
end.

And this is my VB Code:
Private Declare Function SumArray Lib "ddll.DLL" _
    (db() as double) As Double

Sub SumArrayTest()
    Dim n(1000) As Double
    Dim i As Long
    Dim result As Double
    For i = 0 To 1000
        n(i) = 2.1235
    Next
    result = SumArray(n)
    MsgBox "Sum = " & result
End Sub

BUT I get this message!:
"....The Memory could not be read..."

Pls Help
0
Comment
Question by:eabell
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3 Comments
 
LVL 12

Accepted Solution

by:
Lee_Nover earned 50 total points
ID: 6971436
you should either change Function SumArray(ar : OleVariant): double;stdcall;
to make ar a variable like :

Function SumArray(var ar : OleVariant): double;stdcall;
then you can use it with vb like:
Private Declare Function SumArray Lib "ddll.DLL" _
  (db() as double) As Double

like this you pass the variable by reference
and in delphi you accept it by reference with var

or leave delphi interface alone and change vb part

so you have :
Private Declare Function SumArray Lib "ddll.DLL" _
   (ByVal db() as double) As Double

haven't tested but it's how it should be done and it should work :)

if it doesn't work simplay pass a pointer to it like it's done in WinApi
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by:Moondancer
ID: 6975514
Has this helped you?  Assuming so, please convert the comment to the Accepted Answer to grade and close this item and award the points.  If more is needed, let us know.
Thanks,
Moondancer - EE Moderator
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Expert Comment

by:pnh73
ID: 9004161
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Accept answer from Lee_Nover

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Paul (pnh73)
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