iOS 8.3 UIAlertController crashes when trying to add a textfield

Question

I have an iPad app. I am creating an UIAlertController and adding a textfield. It crashes. It only crashes when I add a textfield.

let alert = UIAlertController(title: "Enter Name", message:nil, preferredStyle: UIAlertControllerStyle.Alert);         
alert.addTextFieldWithConfigurationHandler { (textfield:UITextField!) -> Void in
                textfield.placeholder = "Sexy time";

            }
 alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: {(action:UIAlertAction!) -> Void in
      //Some action here   
 }));

 self.presentViewController(alert, animated: true, completion: nil);

I get a fun crash telling me that the constraints are messed up. This code works fine in < 8.3 with no warnings. Even on a clean project with nothing in it but this code, it crashes - The project needs to be a splitview project on iPad.

Here is the full stack trace plus bizarre constraint warnings which appears only after trying to add the textfield to alertController.

2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66cf9e010 UITableView:0x7fb66b855000.right == UIView:0x7fb66fae68e0.right>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.155 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66fb37f90 UITableView:0x7fb66b855000.top == UIView:0x7fb66fae68e0.top>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:07.156 Observation[18235:281813] The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x7fb66fb80580 UITableView:0x7fb66b855000.bottom == UIView:0x7fb66fae68e0.bottom>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView _viewHierarchyUnpreparedForConstraint:] to debug.
2015-04-10 15:25:13.589 Observation[18235:281813] View hierarchy unprepared for constraint.
    Constraint: <NSLayoutConstraint:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left>
    Container hierarchy: 
<UIView: 0x7fb66fa86e00; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf8e0>>
   | <UIView: 0x7fb66af3e080; frame = (0 0; 0 0); clipsToBounds = YES; layer = <CALayer: 0x7fb66fae32c0>>
   |    | <_UIAlertControllerShadowedScrollView: 0x7fb66fa68c80; frame = (0 0; 0 0); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fb66fa38a80>; layer = <CALayer: 0x7fb66fa97560>; contentOffset: {0, 0}; contentSize: {0, 0}>
   |    |    | <UIView: 0x7fb66fa87350; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf810>>
   |    |    |    | <UILabel: 0x7fb66fa88740; frame = (0 0; 0 0); text = 'Enter Name'; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66fa94ed0>>
   |    |    |    | <UILabel: 0x7fb66fa73710; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66cc0ee10>>
   |    |    |    | <UIView: 0x7fb66fae68e0; frame = (0 0; 0 0); clipsToBounds = YES; layer = <CALayer: 0x7fb66fa90160>>
   |    | <UILabel: 0x7fb66fa3ad40; frame = (0 0; 0 0); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fb66fa73680>>
   |    | <UICollectionView: 0x7fb66c130200; frame = (0 0; 0 0); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fb66faebab0>; layer = <CALayer: 0x7fb66fa3acf0>; contentOffset: {0, 0}; contentSize: {0, 0}> collection view layout: <_UIAlertControllerCollectionViewFlowLayout: 0x7fb66fae0b30>
    View not found in container hierarchy: <UITableView: 0x7fb66b855000; frame = (0 20; 768 1004); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x7fb66cf79f30>; layer = <CALayer: 0x7fb66cf600a0>; contentOffset: {0, 0}; contentSize: {768, 25}>
    That view's superview: NO SUPERVIEW
2015-04-10 15:25:13.594 Observation[18235:281813] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to install constraint on view.  Does the constraint reference something from outside the subtree of the view?  That's illegal. constraint:<NSLayoutConstraint:0x7fb66cf9dfc0 UITableView:0x7fb66b855000.left == UIView:0x7fb66fae68e0.left> view:<UIView: 0x7fb66fa86e00; frame = (0 0; 0 0); layer = <CALayer: 0x7fb66fadf8e0>>'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000102940c65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010221dbb7 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000102940b9d +[NSException raise:format:] + 205
    3   Foundation                          0x0000000101daf479 -[NSLayoutConstraint _addToEngine:integralizationAdjustment:mutuallyExclusiveConstraints:] + 187
    4   UIKit                               0x00000001039bca34 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 474
    5   Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    6   UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    7   UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    8   UIKit                               0x00000001039bc933 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 217
    9   Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    10  UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    11  UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    12  UIKit                               0x00000001039bc933 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke_2 + 217
    13  Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    14  UIKit                               0x00000001039bc83a __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 452
    15  UIKit                               0x00000001039bc64d -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 197
    16  UIKit                               0x00000001033b5717 __40-[UIView(Hierarchy) layoutBelowIfNeeded]_block_invoke + 39
    17  Foundation                          0x0000000101dbd1be -[NSISEngine withBehaviors:performModifications:] + 155
    18  UIKit                               0x00000001033b5556 -[UIView(Hierarchy) layoutBelowIfNeeded] + 320
    19  UIKit                               0x000000010374a394 -[_UIAlertControllerAnimatedTransitioning animateTransition:] + 470
    20  UIKit                               0x000000010344fa4e __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 1867
    21  UIKit                               0x000000010336562c _applyBlockToCFArrayCopiedToStack + 314
    22  UIKit                               0x00000001033654a6 _afterCACommitHandler + 533
    23  CoreFoundation                      0x0000000102873ca7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    24  CoreFoundation                      0x0000000102873c00 __CFRunLoopDoObservers + 368
    25  CoreFoundation                      0x0000000102869a33 __CFRunLoopRun + 1123
    26  CoreFoundation                      0x0000000102869366 CFRunLoopRunSpecific + 470
    27  GraphicsServices                    0x0000000106dd6a3e GSEventRunModal + 161
    28  UIKit                               0x0000000103341900 UIApplicationMain + 1282
    29  Observation                         0x0000000101612927 main + 135
    30  libdyld.dylib                       0x0000000104f60145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

Edit: This fix changes depending on if you are building with Xcode 6 or Xcode 7, so I've added the relevant information for both versions of Xcode.

---

I ran into this today and what it's saying is that it can't add the text field to the view controller's view or that it can't add auto-layout constraints to its superview. This seems to be because it hasn't created the superview to add it to yet, and so it all panics and crashes.

Simple fix I found is add the text field after you tell the alert controller to present. That fixed it to me, though I'm not sure if it'll affect anything like the text field popping in as the alert is presenting.

Built with Xcode 6

let alertController = UIAlertController(title: "Enter Name", message:nil, preferredStyle: .Alert)

let okAction = UIAlertAction(title: "Ok", style: .Default) { (_) -> Void in
    // Some action here
}
alertController.addAction(okAction)

presentViewController(alertController, animated: true, completion: nil)

// Add any text fields after presenting the alert controller to fix crash in iOS 8.3
alertController.addTextFieldWithConfigurationHandler { (textfield) -> Void in
    textfield.placeholder = "Name"
}

P.s. As a side note from your code example, remember with Swift, you don't need to use ; at the end of every line, though it doesn't matter if you do. 😉

---

Built with Xcode 7

When you build your app using Xcode 7, it seems like Apple have fixed the issue. Using the method shown above will no longer show a text field in iOS 9 (even though it still shows correctly in iOS 8).

Below is a snippet of code, how it should have been the whole time, and when built in Xcode 7 it runs correctly in iOS 8 and iOS 9.

let alertController = UIAlertController(title: "Enter Name", message:nil, preferredStyle: .Alert)

alertController.addTextFieldWithConfigurationHandler { (textfield) -> Void in
    textfield.placeholder = "Name"
}

let okAction = UIAlertAction(title: "Ok", style: .Default) { (_) -> Void in
    // Some action here
}
alertController.addAction(okAction)

presentViewController(alertController, animated: true, completion: nil)

Tested in Swift 2.0 and Obj-C with Xcode 7 GM (7A218)

Answer 2

This bug is triggered if the UIAlertController's view is loaded when you calling -addTextFieldWithConfigurationHandler: ([alert isViewLoaded] == YES).

If you are accessing alert.view prior to calling -addTextFieldWithConfigurationHandler, move whatever you are doing with alert.view to after the call to -addTextFieldWithConfigurationHandler:.

Answer 3

As @Dex mentioned, I fixed this by modifying my controller's view AFTER adding the text field. I was modifying the view's tint color.

controller.view.tintColor = ...some color...

Moving this to "after" adding the text field fixed it for me. Accepted answer and other suggestions led to other bugs for me. Sorry, I don't have the rep to post a comment yet on @Dex's answer.

Answer 4

This seems to have something to do with styling the UIAlertController's view, as eluded to by @BigShay.

In my example I set the tintColor of the view before adding the UITextField and I crash in iOS 8. The workaround given by @Baza207 to add the UITextField after displaying the alert avoids the crash in iOS 8, however it also results in no text field appearing at all in iOS 9.

If you just move the styling to after adding the text field, it works with both iOS 8 and iOS 9 (no crash in iOS 8, and no missing text field in iOS 9):

Crash in iOS 8

Works in iOS 9

alertController.view.tintColor = UIColor.blueColor()

alertController.addTextFieldWithConfigurationHandler { textField in
}

presentViewController(alertController, animated: true, completion: nil)

Works in iOS 8

No text text field in iOS 9

alertController.view.tintColor = UIColor.blueColor()

presentViewController(alertController, animated: true, completion: nil)

alertController.addTextFieldWithConfigurationHandler { textField in
}

Works in iOS 8

Works in iOS 9

alertController.addTextFieldWithConfigurationHandler { textField in
}

alertController.view.tintColor = UIColor.blueColor()

presentViewController(alertController, animated: true, completion: nil)