NSThread reading parent's ivars?

Question

I detach a new NSThread withObject:self so that the thread can callback the main thread as a delegate. However, I also need the new thread to be able to read some values in the parent. With NSThread, I can only pass one object withObject, and I'm using that to pass self because of the delegate methods. Is there a way my new thread can read values from it's parent? Perhaps through the self object that is passed to it?

Here's where I launch the thread:

MulticastDaemon* multicastDaemon = [[MulticastDaemon alloc] init];
[NSThread detachNewThreadSelector:@selector(doWorkWithDelegate:)
                         toTarget:multicastDaemon
                       withObject:self];

I want to pass a multicast IP address and port number to the daemon, so he knows what to listen on, but I'm not sure how to get those values to multicastDaemon.

How can multicastDaemon access those values?

Answer 1

Yes, you can access the variables by making them properties and then doing something like this (you don't say what the class is that this call is made from, so I've called it MyClass):

@implementation MulticastDaemon

-(void) doWorkWithDelegate:(MyClass*) cls
{
    cls.value1 = 12;
    ...
}

...

@end

EDIT: Corrected implementation.

Answer 2

You'd better use the subclass of NSOperation and then add it to the NSOperationQueue. You can add any additional parameters to that operation subclass.

There is also another advantage of NSOperation over NSThread. NSOperation and NSOperationQueue are build on top of the GCD and threading is far more optimal then NSThread.

But you can also simply add some properties to your MulticastDaemon.

Answer 3

You can change your MulticastDaemon's interface slightly so that you set the delegate before creating the new thread. Then you free up the withObject: slot to pass something else along. This avoids accessing variables across threads.

Either:

 MulticastDaemon* multicastDaemon = [[MulticastDaemon alloc] initWithDelegate:self];
[NSThread detachNewThreadSelector:@selector(doWorkWithInformation:)
                         toTarget:multicastDaemon
                       withObject:operatingInfo];

Or

MulticastDaemon* multicastDaemon = [[MulticastDaemon alloc] init];
[multicastDaemon setDelegate:self];

Otherwise, you'll have to create a method that the daemon can call on its delegate that gathers and packages up the information to pass back. In that case, you'll probably have to start worrying about thread safety.