Asynchronously run an NSThread, but with a delegate?

Question

I want to launch a daemon on new thread, to my program doesn't lock up while waiting for input from the daemon, but I need a way for the main program to get information back from the daemon. I've used NSThread to fire off a new thread, but I don't see how to use a delegate with NSThread.

For more context, I'm working on a custom patch for Quartz Composer that will receive data from the network. The idea is that a second thread could run the daemon, and on each frame, I'd grab the new data from an ivar set by a delegate method when the daemon thread received new data.. all the while, the composition runs along with no interruption.

Can I do this with NSThread? Is there a better way I should be looking at?

Answer 1

Edit: If you want the delegate callbacks to occur on the main thread, use this pattern: [delegate performSelectorOnMainThread:@selector(threadDidSomething:) withObject:self waitUntilDone:NO]

Here you go. I believe this is self-explanatory, but if not, just let me know. Please note: I just wrote this code based on the API, but have not tested it, so take caution.

@protocol ThreadLogicContainerDelegate <NSObject>
- (void)threadLogicContainerDidStart:(ThreadLogicContainer*)theThreadLogicContainer;
- (void)threadLogicContainerDidFinish:(ThreadLogicContainer*)theThreadLogicContainer;
@end

@interface ThreadLogicContainer

- (void)doWorkWithDelegate:(id<ThreadLogicContainerDelegate>)delegate;

@end

@implementation ThreadLogicContainer

- (void)doWorkWithDelegate:(id<ThreadLogicContainerDelegate>)delegate
{
    @autoreleasepool
    {
        [delegate threadLogicContainerDidStart:self];

        // do work

        [delegate threadLogicContainerDidFinish:self];
    }
}

@end


@interface MyDelegate <ThreadLogicContainerDelegate>
@end

@implementation MyDelegate
- (void)threadLogicContainerDidStart:(ThreadLogicContainer*)theThreadLogicContainer
{}
- (void)threadLogicContainerDidFinish:(ThreadLogicContainer*)theThreadLogicContainer
{}
@end

Sample usage:

ThreadLogicContainer* threadLogicContainer = [ThreadLogicContainer new];
[NSThread detachNewThreadSelector:@selector(doWorkWithDelegate:)
                         toTarget:threadLogicContainer
                        withObject:myDelegate];

reference: http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSThread_Class/Reference/Reference.html

Answer 2

You might also want to consider using operation queues (NSOperation) or dispatch queues (GCD) instead of NSThread.

If you haven't already, take a look at Apple's Concurrency Programming Guide; they're really recommending the queue-based approach instead of explicit thread creation.