[Lazarus] Application.QueueAsyncCall and checking if object still exists

[Michael Schnell]

On 09/22/2011 05:28 PM, Krzysztof wrote:
>
> Main problem is: I don't know how to tell thread (which is locked in 
> QueueAsyncCall critical section), that method pointer which he trying 
> to post, doesn't exists anymore.
>
Seemingly you want to create a queue of objects and/or strings that are 
sent from the Thread to the Main thread, and want to be sure that the 
main thread in fact handles all of them.

If just doing a progress indicator, it would not harm if some events in 
the main thread would be dropped, so IMHO it would be a better way to 
use a global integer variable that is written by the thread and read by 
the main thread. So no object or string creation is necessary.

If you really need to dedicatedly handle all events I;HO a good way is 
to use a TThreadList with "add" in the thread.

Another  thing to watch is how the reference counting strings are 
handled. Are they correctly kept life when the function that moves them 
into the object is left ? Are they correctly freed when the object is 
freed ?

I usually try to avoid handling strings in such a creative way.

-Michael