Thread - use of variables 1

[gp4]

I am using Delphi 7 and would like to know if it is possible to read variables that exist in the Thread that is instantiated, from the main code. If so, how should I declare these variables in the threaded code.

N.B my main code is in unit1.pas, and the thread code in unit2.pas for example.
Thanks.

 

[Nordlund]

Hi.
Override the TThread.Create constructor to pass the mainform as an argument.
The MainForm private variable in the thread is called FMainForm in this example;

constructor TThread.Create(CreateSuspended: Boolean; var MainForm: TForm); override;
begin
  FMainForm := MainForm;
  Inherited Create(CreateSuspended);
end;

//Nordlund

 

[gp4]

Hi Nordlund,
Thanks for your feedback.
I guess this allows you to access variables that exist in the mainform, from the new thread.
How would you access the variables in the thread from the main application though?
Thanks

 

[Nordlund]

That's little bit harder to explain.
Somehow you have to keep track of the running threads, maybe in a TList. Then you can create public members in the threads, end then control them by using
TMyThread(List[x]).TheVariable

Explain a little bit more how you're going to use the threads, and why you have to store in them.

//Nordlund

 

[gp4]

Hi Nordlund,
I'm using the thread to do a very large filecopy/cut operation (a few GB) using filestreams.
I wanted to get access to the filestream.pos property in the thread from the main application to determine its progress.

Thanks

 

[roo0047]

Why can't you just put in in a global record?

 

[Nordlund]

Hi.
If you only using one thread, you can access the Filestream by the variable you haved defined for this thread. (MyThread.FileStream.Pos)

Otherwise, if you are 100% sure you will not use another "filecopy" thread you can use a global variable...
But this is not "Threadsafe" due to use of global variables.

I would prefer the first way... Declare a variable for the thread, and make the FileStream public in the thread, then you can access it "propertly"...

//Nordlund

 

[gp4]

Thanks for the help.