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Re: Running an NSTask Within an NSThread

Thanks James,

You were half-right with the over-releasing thing. All my code for running the task is in a TaskController object, which was being autoreleased after the task was run, but before the NSTaskDidTerminate was sent. I'd registered the object as an observer for this notification but not removed is as the observer in the dealloc method for the class! It suddenly occurred to me that a notification was being sent to a dealloc'd object.

Now I have the problem of my taskController being dealloc'd before the task has finished (whether its in a new thread or not) so the NSTaskDidTerminateNotification is not being received by the object. I currently have a class method that instantiates my TaskController object, this is called from my NSDocument subclass. So NSDocument subclass calls:


// NSDocument subclass implementation
- (IBAction)runTask:(id)sender;
{
TaskController *tC = [[TaskController defaultControllerForDocument:self];
[tC performTask];
}


// TaskController.m

+ (TaskController *)defaultController;
{
TaskController *controller = [[self alloc] init];
return [controller autorelease];
}

- (id)init;
{
if (![super init])
	return nil;

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(taskDidTerminate:) name:NSTaskDidTerminateNotification object:nil];
return self;
}

- (void)dealloc;
{
[[NSNotificationCenter defaultCenter] removeObserver:self]; // here's the fix for the crash
[super dealloc];
}

- (void)performTask;
{
task = [[NSTask alloc] init];
//configure task
[task launch];
}

- (void)taskDidTerminate:(NSNotification *)notification;
{
[task release];
task = nil;
// do important stuff
}

This currently adheres to the memory management conventions, and removing the autorelease from the -+defaultControllerForDocument: method and moving it to the -taskDidTerminate: method would solve my problem, but it feels hacky as it goes against the convention (or does it?!). What I need it a more elegant solution. I also need to account for the times when the task does not finish and just waits for user input.

I'm not so sure about using -waitUntilExit as that polls, but thanks for the advice. Any ideas now I've solved the crash?

Thanks,

Jon
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