Question

I’m trying to access an OleVariant in a callback that is coming from an ActiveX library.

Here’s what the event handler is defined as in the TLB:

procedure(ASender: TObject; var structQSnap: {??structVTIQSnap}OleVariant) of object; 

Here’s the definition of structVTIQSnap in the TLB:

structVTIQSnap = packed record   bstrSymbol: WideString;   bstrListingExch: WideString;   bstrLastExch: WideString;   fLastPrice: Double;   nLastSize: Integer;   bstrBbo: WideString;   bstrBidExch: WideString;   fBidPrice: Double;   nBidSize: Integer;   bstrAskExch: WideString;   fAskPrice: Double;   nAskSize: Integer;   fHighPrice: Double;   fLowPrice: Double;   fOpenPrice: Double;   fClosePrice: Double;   nCumVolume: Integer;   bstrTradeCondition: WideString;   nQuoteCondition: Integer;   bstrCompanyName: WideString;   f52WeekHigh: Double;   f52WeekLow: Double;   fEps: Double;   nSharesOutstanding: Integer;   nSpCode: Integer;   fBeta: Double;   bstrExDivDate: WideString;   nDivFreq: Integer;   fDivAmt: Double;   nAvgVolume: Integer;   bstrCusip: WideString;   fVwap: Double;   bstrUpdateTime: WideString;   bstrExch: WideString;   nSharesPerContract: Integer; end; 

It compiles fine, but everytime I try to access the bstrSymbol, I get an ‘Invalid Variant Operation’:

 procedure TForm1.HandleVTIQuoteSnap(ASender: TObject; var structQSnap: OleVariant);  var     symbol: WideString;  begin     symbol := structQSnap.bstrSymbol; // this line causes the exception  end; 

How do I access structQSnap and its properties in Delphi?

In C#, this function works fine for the event handler:

    void vtiQ_OnVTIQSnap(ref vtiLib.structVTIQSnap structQSnap)     {         MessageBox.Show('Got qsnap for ' + structQuoteSnap.bstrSymbol);                 } 

Any ideas?

Answer 1

I think that Delphi’s ActiveX import wizard doesn’t know how to handle the structVTIQSnap type (which seems to be a record) properly and just uses the default OleVariant. Is there a type declaration named structVTIQSnap or similar in the generated …_TLB.pas file? Try using that instead of OleVariant, e.g.

procedure (ASender: TObject; var structQSnap: structVTIQSnap) of object; 

The type will probably be declared as a ‘packed record’.