Re: Question about NSThread?
Re: Question about NSThread?
- Subject: Re: Question about NSThread?
- From: Jean-Daniel Dupas <email@hidden>
- Date: Wed, 19 Nov 2008 23:17:31 +0100
Yes, as long as you do not access directly your UI from the background
thread (you can do it, but using you should use the
performOnMainThread: method).
Note that you may want to release and recreate your auto release pool
from time to time (between each image for example), else your
autoreleased item would not be released before the end of the thread.
Le 19 nov. 08 à 22:37, Jean-Nicolas Jolivet a écrit :
Mmm I see....
Well, right now I would say my worker thread is pretty much just
reading values (size of image to generate etc)... but it's not
"modifying" anything... it doesn't change any variables etc... just
reads the info it needs to generate the images and ...well,
generates the images...
If my worker thread doesn't have to "write" in any variables/objects
whatever, shared with the UI, can I assume that it's safe to leave
it like it is?
On 19-Nov-08, at 4:32 PM, Stefan Sinclair wrote:
In a word, yes :)
If you are accessing a piece of memory across threads, you should
be making sure you are synchronizing any access to that memory
which could occur across threads. For simple primitives (such as
possibly your work progress number) just using an atomic integer
would suffice. For more complicated access, you will want better
protection (such as using locks around any APIs which can access
your data). You're probably getting away with it now b/c your UI
thread (the main thread) is only reading data (the work progress
value - I'm guessing a single integer or floating point value which
can be read/written in a single instruction) while the worker
thread is modifying it. But it doesn't hurt to use proper thread-
safe access patterns for data shared between threads even for small
things like this.
-Stefan
> From: email@hidden
> To: email@hidden
> Date: Wed, 19 Nov 2008 15:57:44 -0500
> Subject: Question about NSThread?
>
> I have an app that generates a bunch of images... the process can
be
> long so I wanted to start it in a separate thread so that the UI
can
> be responsive etc...
>
> basically the only thing I did was:
>
> [NSThread detachNewThreadSelector:@selector(doLongProcess)
> toTarget:self withObject:nil];
>
> and I added
>
> NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
>
> at the beginning of my doLongProcess method, and [pool release]
at the
> end...
> Now the weird part is that... it appears to be working... the
images
> are created...the UI stays responsive..my status textfield gets
> updated (it wasn't getting updated when the long process was not
in a
> separate thread)...
>
> Am I wrong to think that it should've been much more complex than
> that? (With NSLocks and whatnot...) Maybe I should just shut up
and be
> happy that it work, but somehow this doesn't seem right...
>
> Jean-Nicolas Jolivet
> email@hidden
> http://www.silverscripting.com
>
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