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POpresentViewController:animated:completion: always results in two instance of the presented view controller, is it a bug?
 

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  1. POpresentViewController:animated:completion: always results in two instance of the presented view controller, is it a bug?
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    <p>I hooked into the presented view controller's init, loadView, viewDidLoad, viewWillAppear:, viewDidAppear:, viewDidUnload and dealloc method to log out relevant timing info.</p> <p>But it was found that whether <code>presentModalViewController:animated:</code> or <code>presentViewController:animated:completion:</code> will result in two instance of the presented view controller and one of them will soonly be destroyed without anything appeared on screen(loadView and next method hasn't been fired yet).</p> <p>Is it a bug or iOS' view controller transition just works like this?</p> <p>Here is the log info, WDIMMindItemEditViewController is the presented view controller and WDIMMainScreenViewController is the presenting view controller:</p> <blockquote> <p>2012-09-29 16:10:02.615 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller will initialize</p> <p>2012-09-29 16:10:02.639 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller initialized</p> <p>2012-09-29 16:10:02.641 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b94d0> :editing view controller will initialize</p> <p>2012-09-29 16:10:02.645 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b94d0> :editing view controller initialized</p> <p>2012-09-29 16:10:02.835 ideaCal[23450:707] &lt; WDIMMainScreenViewController: 0x27c790> will present modal view controller: &lt; WDIMMindItemEditViewController: 0x2b5260></p> <p>2012-09-29 16:10:02.841 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller load view</p> <p>2012-09-29 16:10:02.910 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller has loaded view</p> <p>2012-09-29 16:10:02.912 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller's view will appear</p> <p>2012-09-29 16:10:03.297 ideaCal[23450:707] &lt; WDIMMainScreenViewController: 0x27c790> will present modal view controller: &lt; WDIMMindItemEditViewController: 0x2b94d0></p> <p>2012-09-29 16:10:03.302 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b94d0> :editing view controller will dealloc</p> <p>2012-09-29 16:10:03.340 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b94d0> :editing view controller ended dealloc</p> <p>2012-09-29 16:10:03.702 ideaCal[23450:707] &lt; WDIMMindItemEditViewController: 0x2b5260> :editing view controller's view appeared</p> <p>2012-09-29 16:10:05.434 ideaCal[23450:707] &lt; WDIMMainScreenViewController: 0x27c790> ended present modal view controller: &lt; WDIMMindItemEditViewController: 0x2b5260></p> </blockquote> <p>And here is my presenting code:</p> <pre><code>- (IBAction)slidingMenuGetPressed:(WZUICircularPagingControlViewSlidingMenu *)slidingMenu event:(UIEvent *)event { WDIMEditViewController * editModalViewController = nil; if ([slidingMenu.identifier isEqualToString:NEW_MIND_ITEM]) { editModalViewController = [[WDIMMindItemEditViewController alloc] init]; } if ([slidingMenu.identifier isEqualToString:NEW_PROJECT]) { editModalViewController = [[WDIMMindItemEditViewController alloc] init]; } if ([slidingMenu.identifier isEqualToString:NEW_TAG]) { editModalViewController = [[WDIMTagEditViewController alloc] init]; } dispatch_queue_t snapshotQueue = dispatch_queue_create("com.WeZZardDesign.ScreenSnapshotQueue", NULL); dispatch_async(snapshotQueue, ^{ UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, self.view.opaque, 0.0); [self.view.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage * snapshot = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); dispatch_async(dispatch_get_main_queue(), ^{ editModalViewController.backgroundImage = snapshot; NSManagedObjectContext * workingContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; workingContext.parentContext = self.database.managedObjectContext; editModalViewController.preference = self.preference; editModalViewController.dataSource = self; editModalViewController.delegate = self; editModalViewController.workingContext = workingContext; NSLog(@"%@ will present modal view controller: %@", self, editModalViewController); [self presentViewController:editModalViewController animated:YES completion:^{ NSLog(@"%@ ended present modal view controller: %@", self, editModalViewController); }]; }); }); dispatch_release(snapshotQueue); } </code></pre> <p>And I have got nothing changed in <code>presentModalViewController:animated:</code> and <code>presentViewController:animated:completion:</code> method.</p>
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      1. POpresentViewController:animated:completion: always results in two instance of the presented view controller, is it a bug?
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    1. COIs looks as if two instances of `WDIMMindItemEditViewController` are initialized in `slidingMenuGetPressed`. Can it be that `NEW_MIND_ITEM` and `NEW_PROJECT` are identical strings? In that case two of the "if" blocks would be executed.
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      1. POpresentViewController:animated:completion: always results in two instance of the presented view controller, is it a bug?
      1. USMartin R
    2. COYes, the `NEW_MIND_ITEM` and `NEW_PROJECT` are identical strings but they are not the same. And not only two instances of `WDIMMindItemEditViewController` were executed, but also `WDIMMainScreenViewController` presented all of them with one of them hasn't call the completion block. It's strange. I think I should create a clean project to rebuild the situation.
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    3. CO1. `isEqualToString:` compares the string contents, not the pointer. So if NEW_MIND_ITEM and NEW_PROJECT are identical strings, then two "if" blocks will be executed. You should check this by setting a breakpoint in the debugger. - 2. "will present modal view controller ..." is shown twice in the NSLog output which means that `slidingMenuGetPressed` has been called twice.
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      1. POpresentViewController:animated:completion: always results in two instance of the presented view controller, is it a bug?
      1. USMartin R
 

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