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pointers, OLEVariant, Arrays of OLEVariant

Posted on 2001-09-13
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Can anybody point me to any documents which clearly explains how to use pointers with OLEVariant and Arrays of OLEVariant. I am being passed parameters of these types from a Server and need to extract the data that is being passed to my program. I am finding it all very confusing.

Thanks.
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Question by:JohnMcGill
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4 Comments
 
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ITugay earned 400 total points
ID: 6479481
Hi JohnMcGill,

you can use typecasting to convert pointer to integer and back.

var
  V: OLEVariant;
  T: TEdit;

begin
  V := Integer(Edit1);

  TEdit(Integer(V)).Text := 'some text';
end;

----
Igor.
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LVL 14

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by:AvonWyss
AvonWyss earned 400 total points
ID: 6479560
Arrays passed along in OLE automation are often pointers to so-called safe arrays (PSafeArray). These are arrays of OLE-compatible variants (OLEVariant). If you get a pointer to a safe array, you can quickly convert it to a OLEVariant array and vice-versa:

function SafeArrayToVariant(SaveArray: PSafeArray): OleVariant;
begin
    TVarData(Result).VType:=varArray;
    TVarData(Result).VArray:=PVarArray(SaveArray);
end;

The other way around goes like this:

function VariantToSafeArray(const Arr: OleVariant): PSafeArray;
begin
   Assert(TVarData(Arr).VType=varArray);
   Result:=PSafeArray(TVarData(Arr).VArray);
end;

[...]
var
    Strings: OleVariant;
    Temp: PSafeArray;
[...]
    {I assume that Temp holds the PSafeArray)
    Strings:=SafeArrayToVariant(Temp);  

And when it is in the Variant, you can just use it like a normal Pascal array...:

   Edit1.Text:=Strings[0];  

Hope this helps!
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by:geobul
ID: 9307969
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