Solved

Sending data using OLE interfaces

Posted on 1998-03-27
3
189 Views
Last Modified: 2010-04-06
I'm writing an ActiveX DLL and I need to send a data structure consisting of a number of classes in a linked list through it's interfaces.  How can I convert this into a data type that OLE can understand?
0
Comment
Question by:BigMadDrongo
3 Comments
 
LVL 4

Expert Comment

by:d003303
ID: 1360964
Yo,
implement the IEnum interface and enumerate through the linked list. The classes you want to pass over should be COM objects with a type library. This as an ultra-short comment. If you have questions, just ask.

Slash/d003303
0
 
LVL 3

Accepted Solution

by:
williams2 earned 200 total points
ID: 1360965
Delphi OLE has a strange understanding of arrays (linked lists). To assign an array to a OleVariant, you need to insert the elements into a TSafeArray. It's a generel suggestion due to the complex handling of variants. (please look up SafeArrays or TSafeArray in the Delphi Help index list). To send special objects, you can first build a record with all simple attributes and send them through the interface as a TSafeArray of Bytes (length = SizeOf(Record) ) and then reassemble the structure. Another approach is to use the class'es .SaveToStream/.LoadFromStream' methods which provides all necessary data in one structure. You could also use the .WriteComponent and .ReadComponent method.
Handling Objects with OLE is not trivial, and the solution generelly depends on which system you want do develop.

Regards
Williams
0
 

Author Comment

by:BigMadDrongo
ID: 1360966
First you have to simplify a datastructure, so you will be able to trace your data's. Stringlists can be saved as one nullterminated string (use the getText function). Try putting all data's you have into one record. I can help you with these routines. I have tested them, and they work fine.

The Addr is the address pointer to the record. (Like ^Record).

  Function RecToOleVariant(Addr: Pointer; Const RSize: Word): OleVariant;
  var
    p: PByteArray;
    i: Integer;
  Begin
    Result:= VarArrayCreate([0, RSize-1], varByte);
    p:= Addr;
    For i:= 0 to RSize-1 do Result[i]:= p[i];
  End;

  Procedure OleVariantToRec(Data: OleVariant; addr: Pointer; RSize: Word);
  var
    p: PByteArray;
    i: Integer;
  Begin
    p:= addr;
    For i:= 0 to RSize-1 do p[i]:= Data[i];
  End;

When you use linked lists (chained lists), you should consider a record ID (Identifing a class) and build up your data by some recursive method.

If like to know more, please leave a comment.

Regards
Williams
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
Hi friends,  in this video  I'll show you how new windows 10 user can learn the using of windows 10. Thank you.
As a trusted technology advisor to your customers you are likely getting the daily question of, ‘should I put this in the cloud?’ As customer demands for cloud services increases, companies will see a shift from traditional buying patterns to new…

911 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

22 Experts available now in Live!

Get 1:1 Help Now