performSegueWithIdentifier需要超过一分钟才能执行，或者会崩溃。

Question

在Xcode 5.0.2中，我创建了一个简单的iPhone应用程序（源代码可在GitHub上获得），该应用程序带有导航控制器，首先显示一个包含Facebook oAuth对话框的Web视图，并且 - 一旦用户已经被认证并且其详细信息已被获取 - 尝试推送DetailViewController：

在上面的故事板中，我已经称之为segue，并在ViewController.m中通过以下代码将其推送：

[self performSegueWithIdentifier: @"segue" sender: self];

NSLog(@"id: %@", dict[@"id"]);
NSLog(@"first_name: %@", dict[@"first_name"]);
NSLog(@"last_name: %@", dict[@"last_name"]);
NSLog(@"gender: %@", dict[@"gender"]);
NSLog(@"city: %@", dict[@"location"][@"name"]);

Facebook用户数据已成功获取并几乎立即打印出来：

id: 597287941
first_name: Alexander
last_name: Farber
gender: male
city: Bochum, Germany

但是有时在进行转换之前会等待约一分钟，或者有时甚至会因为以下错误而崩溃：

2014-01-09 22:11:29.017 oauthFacebook[4012:1403] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<DetailViewController 0x8a89cd0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key id.'
*** First throw call stack:
(
    0   CoreFoundation                      0x0173b5e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x014be8b6 objc_exception_throw + 44
    2   CoreFoundation                      0x017cb6a1 -[NSException raise] + 17
    3   Foundation                          0x0117f9ee -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
    4   Foundation                          0x010ebcfb _NSSetUsingKeyValueSetter + 88
    5   Foundation                          0x010eb253 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 267
    6   Foundation                          0x0114d70a -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 412
    7   UIKit                               0x004cea15 -[UIRuntimeOutletConnection connect] + 106
    8   libobjc.A.dylib                     0x014d07d2 -[NSObject performSelector:] + 62
    9   CoreFoundation                      0x01736b6a -[NSArray makeObjectsPerformSelector:] + 314
    10  UIKit                               0x004cd56e -[UINib instantiateWithOwner:options:] + 1417
    11  UIKit                               0x0033f605 -[UIViewController _loadViewFromNibNamed:bundle:] + 280
    12  UIKit                               0x0033fdad -[UIViewController loadView] + 302
    13  UIKit                               0x003400ae -[UIViewController loadViewIfRequired] + 78
    14  UIKit                               0x003405b4 -[UIViewController view] + 35
    15  UIKit                               0x0035a3e2 -[UINavigationController _startCustomTransition:] + 778
    16  UIKit                               0x003670c7 -[UINavigationController _startDeferredTransitionIfNeeded:] + 688
    17  UIKit                               0x00367cb9 -[UINavigationController __viewWillLayoutSubviews] + 57
    18  UIKit                               0x004a1181 -[UILayoutContainerView layoutSubviews] + 213
    19  UIKit                               0x00297267 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
    20  libobjc.A.dylib                     0x014d081f -[NSObject performSelector:withObject:] + 70
    21  QuartzCore                          0x03b492ea -[CALayer layoutSublayers] + 148
    22  QuartzCore                          0x03b3d0d4 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
    23  QuartzCore                          0x03b3cf40 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
    24  QuartzCore                          0x03aa4ae6 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
    25  QuartzCore                          0x03aa5e71 _ZN2CA11Transaction6commitEv + 393
    26  QuartzCore                          0x03aa60c2 _ZN2CA11Transaction14release_threadEPv + 226
    27  libsystem_pthread.dylib             0x01e7681c _pthread_tsd_cleanup + 93
    28  libsystem_pthread.dylib             0x01e7327e _pthread_exit + 108
    29  libsystem_pthread.dylib             0x01e73dd8 pthread_workqueue_setdispatchoffset_np + 0
    30  libsystem_pthread.dylib             0x01e77cce start_wqthread + 30
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

这种行为的原因可能是什么呢？

更新：

我已经按照Savana的建议清理了IBOutlets，但应用程序仍然崩溃：

2014-01-10 10:26:59.379 oauthFacebook[4342:4113] bool _WebTryThreadLock(bool), 0x8be2960: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   0x51481ae WebThreadLock
2   0x452a57 -[UIWebDocumentView _responderForBecomeFirstResponder]
3   0x27da9e -[UIView setUserInteractionEnabled:]
4   0x934d72 -[_UIViewControllerTransitionContext _disableInteractionForViews:]
5   0x368573 -[UINavigationController pushViewController:transition:forceImmediate:]
6   0x3680b5 -[UINavigationController pushViewController:animated:]
7   0x770c65 -[UIStoryboardPushSegue perform]
8   0x76107e -[UIStoryboardSegueTemplate _perform:]
9   0x342280 -[UIViewController performSegueWithIdentifier:sender:]
10  0x29f0 __32-[ViewController fetchFacebook:]_block_invoke
11  0x11da695 __67+[NSURLConnection sendAsynchronousRequest:queue:completionHandler:]_block_invoke_2
12  0x113a945 -[NSBlockOperation main]
13  0x1193829 -[__NSOperationInternal _start:]
14  0x1110558 -[NSOperation start]
15  0x1195af4 __NSOQSchedule_f
16  0x1ae74b0 _dispatch_client_callout
17  0x1ad4018 _dispatch_async_redirect_invoke
18  0x1ae74b0 _dispatch_client_callout
19  0x1ad5eeb _dispatch_root_queue_drain
20  0x1ad6137 _dispatch_worker_thread2
21  0x1e73dab _pthread_wqthread
22  0x1e77cce start_wqthread
(lldb) 

当我在performSegueWithIdentifier调用之前添加assert（[NSThread isMainThread]）;时，我可以看到这不是主线程...

调用performSegueWithIdentifier是否需要在主线程上执行？

- Alexander Farber

---

问题出在你的DetailViewController中。可能有几个原因...但首先我会检查一下DetailViewController中的IBOutlets和IBActions，确保你没有连接到一个不存在的IBOutlet或IBAction。 - Lyndsey Scott

Answer 1

我已经能够通过这段代码解决我的问题（即详细视图控制器在延迟后显示或应用程序崩溃）：

我使用以下代码解决了我的问题：

         dispatch_async(dispatch_get_main_queue(), ^(void) {
             [self performSegueWithIdentifier: @"segue" sender: self];
         });

- Alexander Farber

---

作为建议，永远不要在非主队列中进行与UI相关的调用。 - The dude

Answer 2

我已经下载并仔细检查了你的故事板，发现在详细视图控制器中有一个从第一个文本字段到用户ID和ID的插座，但是在代码中没有IBoutlet，请删除故事板中的ID IBOutlet。

- savana

---

好的，谢谢 - 但我现在还没有使用那些插座（只需使用 NSLog 打印数据）。这可能是一个线程问题吗 - 因为我从 Facebook 回调中调用了 performSegueWithIdentifier？ - Alexander Farber

没有问题，拔掉插座它就能正常工作。 - savana