Solved

Using threads

Posted on 1998-06-07
4
139 Views
Last Modified: 2010-05-18
I need to write a simple program that uses another thread..
I've done this in C++ builder without any problems, but I seem to be getting something wrong doing this with Delphi..

Here's some of my code:
type
  newthread = class(TThread)
  private
    { Private declarations }
  protected
    procedure Execute; override;
  public
    procedure formrepaint;
  end;

implementation
uses Unit1;

procedure newthread.Execute;
var
cont : boolean;
begin
cont := true;
  while (cont) do
  begin
   Synchronize(Formrepaint);
   if terminated then
    cont := false;
  end;
end;

procedure newthread.formrepaint;
begin
mainform.repaint;
end;

now, the problem I'm having is somewhere at the other end (I think)... in mainform, I have the code
var
  other : newthread;
...
other.create(false);
...
{here I have some code that accesses and does some changes to the mainform}
...
other.destroy;

I'm certain that my mistake is a small and stupid one that would be obvious to someone who know how to use threads in Delphi... please HELP.

The program always crashes where I call the create method... what am I missing????

Thanks in advance...
0
Comment
Question by:rafy
  • 2
4 Comments
 
LVL 5

Expert Comment

by:julio011597
ID: 1351256
Can yo show your exact error message... or whatever you get upon calling create()?

Also, there seems to be no reason for such a behaviour in the code you've posted... is that all?

Regards, julio
0
 

Author Comment

by:rafy
ID: 1351257
The error I'm getting is a
"Access violation at address..."
Do I have to define create??

Note: I also get a compiler warning telling me that variable "other" may not be initialized (?)
0
 
LVL 5

Accepted Solution

by:
inter earned 100 total points
ID: 1351258
Hi there,
The problem is basic and nothing to do with threads. Any pascal class INSTANCE can not be created as
    ...
    other.create(false);
    ...
the correct way is
    other := newthread.Create(false);
Upon destruction of the thread call Terminate first then Free(not Destroy it is an ill practice for VCL.)

   other.terminate;
   other.free;
Regards, Igor
0
 

Author Comment

by:rafy
ID: 1351259
Perfect!... I was so certain it was something simple like that... Thanks again
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

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

The uses clause is one of those things that just tends to grow and grow. Most of the time this is in the main form, as it's from this form that all others are called. If you have a big application (including many forms), the uses clause in the in…
This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
This tutorial gives a high-level tour of the interface of Marketo (a marketing automation tool to help businesses track and engage prospective customers and drive them to purchase). You will see the main areas including Marketing Activities, Design …
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

773 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