Thread handling issue

[Cameron Simpson]

On 07Oct2011 10:15, Paul <poalman at gmail.com> wrote:
| Tim Golden <mail <at> timgolden.me.uk> writes:
| > On 07/10/2011 09:29, Paul wrote:
| > > My problem is if the user doesn't select an output location and cancels the
| > > dialog to go back to the selection I want to terminate the thread to avoid the
| > > user opening and closing the output selection firing off a ton of threads.
| > >
| > > As there's no inbuilt way of killing threads I was wondering the best way to
| > > prevent this?
| > 
| > The most common approach is to have the thread monitor an event which is
| > set if, for example, the user cancels. The thread may of course have to
| > wait, for example, for a long-running database query to complete before
| > it can discover that its time has been wasted :)
[...]
| My first thought was to use a flag but wouldn't the new thread see the cancel 
| flag and stop as well? I could set it back but then any other threads might have 
| been busy and not seen it while the flag was on.

I'd be inclined to dispatch threads via a control object of some kind.
You'd have a default one for your program as a whole, but when you have
a circumstance such as you describe instantiate a new control object.
Set the cancel flag in the control objects. Have threads poll their
invoking control object. That way you can have a flag that applies to
your desired set of threads.

Cheers,
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

He's silly and he's ignorant, but he's got guts, and guts is enough.
        - Sgt. Hartmann