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amith
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 Posted: Tue Nov 04, 2003 4:42 am Post subject: Copy an object into a VARIANT??? |
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Hai all,
I need to pass VARIANT which holds an object as one of the parameter from
COM client. I need to reconstruct back the object from the VARIANT in the
server. How do I copy a user defined object into a VARIANT or OleVariant?
and reconstruct back at the server end?
Please advice.
--
Amith.
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Deborah Pate (TeamB)
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| Posted: Tue Nov 04, 2003 11:27 am Post subject: Re: Copy an object into a VARIANT??? |
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<
I need to pass VARIANT which holds an object as one of the
parameter from COM client.
The COMish thing to do is to use interfaces - make your
object implement an interface and pass that.
You can also pass your object's data as a variant array of
bytes, and reconstitute it at the other end. If you do
that, though, you obviously need to make sure that you
don't accidentally pass any pointers instead.
--
Deborah Pate (TeamB) http://delphi-jedi.org
TeamB don't see posts sent via Google or ISPs
Use the real Borland server: newsgroups.borland.com
http://www.borland.com/newsgroups/genl_faqs.html
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amith
Guest
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| Posted: Wed Nov 05, 2003 6:10 am Post subject: Re: Copy an object into a VARIANT??? |
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Hai Deborah,
Many thanks for your suggestions  .
Regarding your second suggestion:
<
You can also pass your object's data as a variant array of
bytes >>
Do you mean to say that i have to copy my object into a SafeArray and then
copy the SafeArray into the variant?
One more question is: My COM method accepts OleVariant as a parameter. But I
am using TVariantArg and TSafeArrayBound for putting the object in to the
safearray and then to variant. OleVariant and TVariantArg are incompatible.
How do i do the conversion?
sample snippet:
VntSal: TVariantArg;
SalObj: TgtSalClass;
bound: TSafeArrayBound;
nBytes: Integer;
pDest: pointer;
nBytes := SizeOf(SalObj);
bound.lLbound := 0;
bound.cElements := nBytes;
VntSal.vt := VT_UI1 or VT_ARRAY;
VntSal.parray := SafeArrayCreate(VT_UI1, 1, bound);
SafeArrayAccessData(VntSal.parray, pDest);
CopyMemory(pDest, addr(SalObj), nBytes);
SafeArrayUnaccessData(VntSal.parray);
gtMyComponentXX1.SetSal(VntSal); --> my COM method accepts OleVariant, i
cannot pass TVariantArg
Please give your thoughts.
--
Amith.
"Deborah Pate (TeamB)" <d.pate (AT) blueyonder (DOT) co.not-this-bit.uk> wrote in
message news:VA.00001d9f.0a6b5102 (AT) blueyonder (DOT) co.not-this-bit.uk...
| Quote: | Amith:
I need to pass VARIANT which holds an object as one of the
parameter from COM client.
The COMish thing to do is to use interfaces - make your
object implement an interface and pass that.
You can also pass your object's data as a variant array of
bytes, and reconstitute it at the other end. If you do
that, though, you obviously need to make sure that you
don't accidentally pass any pointers instead.
--
Deborah Pate (TeamB) http://delphi-jedi.org
TeamB don't see posts sent via Google or ISPs
Use the real Borland server: newsgroups.borland.com
http://www.borland.com/newsgroups/genl_faqs.html
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Deborah Pate (TeamB)
Guest
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| Posted: Wed Nov 05, 2003 12:29 pm Post subject: Re: Copy an object into a VARIANT??? |
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<
Do you mean to say that i have to copy my object into a
SafeArray and then copy the SafeArray into the variant?
No, you don't need to use SafeArray functions, you can use
Delphi's variant routines. Here are a couple of functions
showing how to put a memorystream into and out of a
variant, as a variant array of bytes:
function MemoryStreamToOleVariant(const Strm:
TMemoryStream): OleVariant;
var
Data: PByteArray;
begin
Result := VarArrayCreate ([0, Strm.Size - 1], varByte);
Data := VarArrayLock(Result);
try
Strm.Position := 0;
Strm.ReadBuffer(Data^, Strm.Size);
finally
VarArrayUnlock(Result);
end;
end;
function OleVariantToMemoryStream(const OV: OleVariant):
TMemoryStream;
var
Data: PByteArray;
Size: integer;
begin
Result := TMemoryStream.Create;
try
Size := VarArrayHighBound (OV, 1) - VarArrayLowBound
(OV, 1) + 1;
Data := VarArrayLock(OV);
try
Result.Position := 0;
Result.WriteBuffer(Data^, Size);
finally
VarArrayUnlock(OV);
end;
except
Result.Free;
Result := nil;
end;
end;
--
Deborah Pate (TeamB) http://delphi-jedi.org
TeamB don't see posts sent via Google or ISPs
Use the real Borland server: newsgroups.borland.com
http://www.borland.com/newsgroups/genl_faqs.html
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amith
Guest
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| Posted: Thu Nov 06, 2003 10:47 am Post subject: Re: Copy an object into a VARIANT??? |
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Hai Deborah,
Thanks a lot for your suggestion.
--
Amith.
"Deborah Pate (TeamB)" <d.pate (AT) blueyonder (DOT) co.not-this-bit.uk> wrote in
message news:VA.00001da4.0049bdce (AT) blueyonder (DOT) co.not-this-bit.uk...
| Quote: | Amith:
Do you mean to say that i have to copy my object into a
SafeArray and then copy the SafeArray into the variant?
No, you don't need to use SafeArray functions, you can use
Delphi's variant routines. Here are a couple of functions
showing how to put a memorystream into and out of a
variant, as a variant array of bytes:
function MemoryStreamToOleVariant(const Strm:
TMemoryStream): OleVariant;
var
Data: PByteArray;
begin
Result := VarArrayCreate ([0, Strm.Size - 1], varByte);
Data := VarArrayLock(Result);
try
Strm.Position := 0;
Strm.ReadBuffer(Data^, Strm.Size);
finally
VarArrayUnlock(Result);
end;
end;
function OleVariantToMemoryStream(const OV: OleVariant):
TMemoryStream;
var
Data: PByteArray;
Size: integer;
begin
Result := TMemoryStream.Create;
try
Size := VarArrayHighBound (OV, 1) - VarArrayLowBound
(OV, 1) + 1;
Data := VarArrayLock(OV);
try
Result.Position := 0;
Result.WriteBuffer(Data^, Size);
finally
VarArrayUnlock(OV);
end;
except
Result.Free;
Result := nil;
end;
end;
--
Deborah Pate (TeamB) http://delphi-jedi.org
TeamB don't see posts sent via Google or ISPs
Use the real Borland server: newsgroups.borland.com
http://www.borland.com/newsgroups/genl_faqs.html
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