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POUpdating an NSmenu from an asynchronous NSURLConnection
 

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  1. POUpdating an NSmenu from an asynchronous NSURLConnection
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    <p>I am writing a little systray application that fetches data from an API and updates its menu accordingly, and am having trouble with updating the menu while it's open.</p> <p>I don't even know where to start, so let's start with the beginning.</p> <p>I have a custom <code>PNLinksLoader</code> class whose responsibility is to fetch the data and parse it:</p> <pre><code>- (void)loadLinks:(id)sender { // instance variable used by the NSXMLParserDelegate implementation to store data links = [NSMutableArray array]; [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) { NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; parser.delegate = self; if (YES == [parser parse]) { NSArray *modes = [NSArray arrayWithObject:NSRunLoopCommonModes]; [delegate performSelectorOnMainThread:@selector(didEndLoadLinks:) withObject:links waitUntilDone:NO modes:modes]; } }]; } </code></pre> <p>The loader is ran one time at the application's startup (works perfectly), and then a timer is setup for periodic refresh:</p> <pre><code>loader = [[PNLinksLoader alloc] init]; [loader setRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://papyrus.pandanova.com/links"]]]; [loader setDelegate:self]; [loader loadLinks:self]; NSMethodSignature *signature = [loader methodSignatureForSelector:@selector(loadLinks:)]; NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature]; [invocation setTarget:loader]; [invocation setSelector:@selector(loadLinks:)]; NSTimer *timer = [NSTimer timerWithTimeInterval:10 invocation:invocation repeats:YES]; [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes]; </code></pre> <p>Now whenever the loader loads new data on the server, if the menu is closed, then everything is ok, I open the menu and the new data is there.</p> <p>But if the menu happens to be open during the refresh, then nothing happens. If I close and reopen the menu, then I can see the new data.</p> <p>I think I'm missing something about the RunLoop, but I fail to see what (my understanding of it is very sparse, as I'm actually writing this little app mainly to learn Objective-C).</p> <p><strong>EDIT</strong></p> <p>The problem here is not to update the menu while it is open, it actually kind of works when I use <code>performSelector:withObject:</code> instead of <code>performSelectorOnMainThread:withObject:waitUntilDone:modes:</code> in the loader. The thing is when I do that I get weird results when updating the menu while it's open (works perfectly when the menu is closed):</p> <p><img src="https://i.stack.imgur.com/ScQZJ.png" alt="weird behavior"></p> <p>Adding an <code>NSLog</code> call in my menu population loop <code>fixes</code> the symptoms, and from what I read on the internet, it might be a sign that I have a race condition on my threads (that's why I tried using <code>performSelectorOnMainThread</code>, but I can't seem to figure it out.</p>
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    1. USGeoffrey Bachelet
    1. USGeoffrey Bachelet
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    1. COPossible duplicate of [Updating an NSmenu from an asynchronous NSURLConnection](http://stackoverflow.com/questions/2808016/how-does-apple-update-the-airport-menu-while-it-is-open-how-to-change-nsmenu-w)
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    2. COI don't think so, see edits in question for more details
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      1. USGeoffrey Bachelet
 

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