There are two basic ways to send a string, seeing as we are talking
postmessage,
here is the fugly one.
p:phar;
GetMem(p,length(data));
move(data[1],p^,length(data));
postmessage(bla bla , integer(p));
remember to free mem on the other side.
Better and nicer way
TString = class(TObject)
property data:string;
end;
Create and send a reference to this, and free it when you are finished.
remember none of these options is safe outside of your own application.
On Thu, 24 Nov 2005 17:43:51 +1300, Rohit Gupta <[EMAIL PROTECTED]> wrote:
I cant see how it can be safe. I was stumped as well when I wanted
to send a string in a message. I had to abandon my ideas.... :-( Let
me know if you have any joy.
From: "Paul Lowman" <[EMAIL PROTECTED]>
To: "Delphi List" <[email protected]>
Date sent: Thu, 24 Nov 2005 16:22:04 +1300
Copies to:
Subject: [DUG] Reference counting
Send reply to: NZ Borland Developers Group - Delphi List
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Heres one for the gurus -
Assume a long string variable is declared locally to a method and is
assigned a string and the string variable is then typecast as an integer
and
used in - say - a windows message by assigning it to the message lparam.
The question is when the message is received by another form / thread is
it
valid to then typecast the lparam back to a string and use it ?
I have tried many variations of this scenario and it seems to work OK
but am
uneasy about whether or not this is safe. I assume it isn't as the local
string variable (which points to the actual string) is on the stack and
is
not maintained after the method is exited but what I really am concerned
about is the reference count for the string - has it been increased by
typecasting it to an integer / pointer whatever ...
I have used some of Marco Cantu's code to try and examine the strings
reference count and it always appears to be -1 if the string is a local
variable although it works correctly for field or global.
All very confusing :-)
I would like to know how the code knows when to inc / dec / dispose the
stirng / array reference count.
Cheers
Paul Lowman
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Rohit
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