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POreadInBackgroundAndNotify method not updating until NSTask complete
 

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  1. POreadInBackgroundAndNotify method not updating until NSTask complete
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    <p>I am trying to run a NSTask in a background thread and display its output in a NSTextview that is on a NSPanel attached to my window ( Preference Pane ) using readInBackgroundAndNotify It does not seem like I am receiving the notifications as the method that should be called is not.</p> <p>I have the controller class (PreferencePane.m) init the class (Inventory.m) that is in charge of running the NSTask</p> <pre><code>- (IBAction)updateInventoryButtonPressed:(id)sender { inventory = [[Inventory alloc] init]; .... </code></pre> <p>Then I send it a NSNotification to start the background (from PreferencePane.m):</p> <pre><code>.... [[NSNotificationCenter defaultCenter] postNotificationName:NotificationInventoryRequested object:self]; } </code></pre> <p>This class (Inventory.m) is an observer of this constant (NotificationInventoryRequested) in its init override</p> <pre><code> - (id)init { [super init]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(inventoryRequested:) name:NotificationInventoryRequested object:nil]; return self; } </code></pre> <p>This runs the inventoryRequested method (of Inventory.m)</p> <pre><code>-(void)inventoryRequested:(NSNotification*)aNotification { if (inventoryIsRunning) { NSLog(@"Inventory is already running, ignoring request"); } else { NSLog(@"Starting Inventory in background..."); [NSThread detachNewThreadSelector:@selector(runInventoryTask) toTarget:self withObject:nil]; } } </code></pre> <p>This runs my NSTask method which I have refactored a few times from examples</p> <p>Set a BOOL to help with duplicate runs sanity is handled by inventoryRequested using ivar inventoryIsRunning</p> <pre><code> -(void)runInventoryTask { inventoryIsRunning = YES; .... </code></pre> <p>I double check my task and setup the readInBackgroundAndNotify adding my self as an observer.</p> <pre><code> .... if (task) { NSLog(@"Found existing task...releasing"); [task release]; } task = [[NSTask alloc] init]; NSLog(@"Setting up pipe"); [task setStandardOutput: [NSPipe pipe]]; [task setStandardError: [task standardOutput]]; // Setup our arguments [task setLaunchPath:@"/usr/bin/local/inventory"]; [task setArguments:[NSArray arrayWithObjects:@"--force", nil]]; //Said to help with Xcode now showing logs //[task setStandardInput:[NSPipe pipe]]; [self performSelectorOnMainThread:@selector(addLogText:) withObject:@"Launching Task..." waitUntilDone:false]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(readPipe:) name: NSFileHandleReadCompletionNotification object: [[task standardOutput] fileHandleForReading]]; [[[task standardOutput] fileHandleForReading] readInBackgroundAndNotify]; [task launch]; [task waitUntilExit]; // Let Any Observers know we are finished with Inventory [[NSNotificationCenter defaultCenter] postNotificationName:NotificationInventoryComplete object:self]; inventoryIsRunning = NO; } </code></pre> <p>This all seems to run fine. But this method never gets called (i.e. I don't see the window update or the NSLog in the console ):</p> <pre><code>-(void)readPipe:(NSNotification *)notification { NSData *data; NSString *text; NSLog(@"Read Pipe was called"); data = [[notification userInfo] objectForKey:NSFileHandleNotificationDataItem]; if ([data length]){ text = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]; // Update the text in our text view [self performSelectorOnMainThread:@selector(addLogText:) withObject:text waitUntilDone:false]; NSLog(@"%@",text); [text release]; } [[notification object] readInBackgroundAndNotify]; } </code></pre> <p>This all seems to run fine. But this method never gets called (i.e. I don't see the window update or the NSLog in the console ). I saw this <a href="https://stackoverflow.com/questions/1324152/nsfilehandle-readinbackgroundandnotify-does-not-work&quot;thread">thread</a> and thought maybe it was my NSPanel blocking the run loop, so I set it as non-modal. I also remember reading about NSNotification's not being synchronous, so I thought perhaps because the method I is being called by a NSNotification, to test I just did this real quick:</p> <pre><code>- (IBAction)updateInventoryButtonPressed:(id)sender { inventory = [[Inventory alloc] init]; /*[[NSNotificationCenter defaultCenter] postNotificationName:NotificationInventoryRequested object:self];*/ [inventory inventoryRequested:self]; [self showPanel:sender]; </code></pre> <p>Obviously self is not valid there, but it served to show me that even calling this method directly did not seem to help ( thus making me think this is not about NSNotification "blocking".)</p> <p>Any thoughts on what I am missing, i have checked for removeObserver anywhere in my code ( I know I need to add it to dealloc and probably in readPipe: when the command run is done). If it helps here is the little NSTextview wrapper which needs work as I does not do line \n in the strings right now.</p> <p>Inventory.h</p> <pre><code>//NSTextview IBOutlet NSTextView * inventoryTextView; </code></pre> <p>Inventory.m</p> <pre><code>-(void)addLogText:(NSString *)text { NSRange myRange = NSMakeRange([[inventoryTextView textStorage] length], 0); [[inventoryTextView textStorage] replaceCharactersInRange:myRange withString:text]; } </code></pre> <p>Any help with this would be appreciated too as its my next stumbling block.</p> <p>UPDATED: Looks like this readData method is being called, however its not updating my Textview until the NSTask is complete,so I have a flow control problem.</p>
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    1. COShameless plug time! I wrote an entire replacement for (most of) NSTask so as not to deal with all that `readInBackgroundAndNotify` folderol ever again: https://bitbucket.org/boredzo/prhtask/
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    2. CO+1 because your question was so detailed it helped me solve a completely unrelated problem.
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