Passing variables between view controllers using segue - crash

Question

I've been trying to pass variables between view controllers without much luck. I started to work backwards from the problem I was encountering but am now having problems just getting the segue to action.
Whether I perform the segue with identifier method or have it actioning from the button I am using to perform a calculation I get the below error in the debugger.
Any help would be appreciated.
2014-02-14 13:59:58.795 BatteryCalculator[6944:70b] Cannot find executable for CFBundle 0x8dbd110 </Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.sdk/System/Library/AccessibilityBundles/CertUIFramework.axbundle> (not loaded)
2014-02-14 14:00:00.869 BatteryCalculator[6944:70b] -[DetectorSpacing _setViewDelegate:]: unrecognized selector sent to instance 0x8dd6ff0
2014-02-14 14:00:00.872 BatteryCalculator[6944:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[DetectorSpacing _setViewDelegate:]: unrecognized selector sent to instance 0x8dd6ff0'
*** First throw call stack:
(
0 CoreFoundation 0x0173d5e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x014c08b6 objc_exception_throw + 44
2 CoreFoundation 0x017da903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x0172d90b ___forwarding___ + 1019
4 CoreFoundation 0x0172d4ee _CF_forwarding_prep_0 + 14
5 UIKit 0x00347ecc +[UIViewController setViewController:forView:] + 40
6 UIKit 0x00342921 -[UIViewController setView:] + 511
7 Foundation 0x010edd28 _NSSetUsingKeyValueSetter + 133
8 Foundation 0x010ed253 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 267
9 Foundation 0x0114f70a -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 412
10 UIKit 0x004d0a15 -[UIRuntimeOutletConnection connect] + 106
11 libobjc.A.dylib 0x014d27d2 -[NSObject performSelector:] + 62
12 CoreFoundation 0x01738b6a -[NSArray makeObjectsPerformSelector:] + 314
13 UIKit 0x004cf56e -[UINib instantiateWithOwner:options:] + 1417
14 UIKit 0x00341605 -[UIViewController _loadViewFromNibNamed:bundle:] + 280
15 UIKit 0x00341dad -[UIViewController loadView] + 302
16 UIKit 0x003420ae -[UIViewController loadViewIfRequired] + 78
17 UIKit 0x003425b4 -[UIViewController view] + 35
18 UIKit 0x0035c3e2 -[UINavigationController _startCustomTransition:] + 778
19 UIKit 0x003690c7 -[UINavigationController _startDeferredTransitionIfNeeded:] + 688
20 UIKit 0x00369cb9 -[UINavigationController __viewWillLayoutSubviews] + 57
21 UIKit 0x004a3181 -[UILayoutContainerView layoutSubviews] + 213
22 UIKit 0x0ecdc56f -[UILayoutContainerViewAccessibility(SafeCategory) layoutSubviews] + 50
23 UIKit 0x00299267 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
24 libobjc.A.dylib 0x014d281f -[NSObject performSelector:withObject:] + 70
25 QuartzCore 0x03b4b2ea -[CALayer layoutSublayers] + 148
26 QuartzCore 0x03b3f0d4 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
27 QuartzCore 0x03b3ef40 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
28 QuartzCore 0x03aa6ae6 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
29 QuartzCore 0x03aa7e71 _ZN2CA11Transaction6commitEv + 393
30 QuartzCore 0x03aa8544 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 92
31 CoreFoundation 0x017054ce __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
32 CoreFoundation 0x0170541f __CFRunLoopDoObservers + 399
33 CoreFoundation 0x016e3344 __CFRunLoopRun + 1076
34 CoreFoundation 0x016e2ac3 CFRunLoopRunSpecific + 467
35 CoreFoundation 0x016e28db CFRunLoopRunInMode + 123
36 GraphicsServices 0x036e29e2 GSEventRunModal + 192
37 GraphicsServices 0x036e2809 GSEventRun + 104
38 UIKit 0x0022ed3b UIApplicationMain + 1225
39 BatteryCalculator 0x0000582d main + 141
40 libdyld.dylib 0x01d7b70d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
At the moment I'm not trying to pass anything, I took that code out temporarily while trying to locate the problem. All I'm doing is calling a segue with identifier and getting the crash. I've also tried just calling the segue from a button on the first view controller but the same error.
When calling the segue with code I was using:
[self performSegueWithIdentifier:#"ResultSegue" sender:sender];

Answer 1

Here is how I pass managedObjectContext between segues
In your class where you will pass the data use prepareForSegue call. (The assumption is this class has a variable called _managedObjectContext which can be passed along to the segue class)
Class to Segue From:
.h file:
#property (weak, nonatomic) NSManagedObjectContext *managedObjectContext;
.m file:
#synthesize managedObjectContext
The call to #synthesize will make the following:
a local variable called _managedObjectContext
a method to getManagedObjectContext
a method to setManagedObjectContext
Additionally add the following method to your class
// Pass on managedObjectContext
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// If the destination VC is able to take the setManagedObjectContext method the current objectContext will be passed along.
if ([segue.destinationViewController respondsToSelector:#selector(setManagedObjectContext:)]) {
[segue.destinationViewController performSelector:#selector(setManagedObjectContext:)
withObject:_managedObjectContext];
} else {
NSLog(#"Segue to controller [%#] that does not support passing managedObjectContext", [segue destinationViewController]);
}
}
Then in my "class" to receive the data I do:
in the .h file i have
#property (weak, nonatomic) NSManagedObjectContext *managedObjectContext;
and in the .m file i have:
#synthesize managedObjectContext;
What this does (with syntehsiation) is make a setManagedObjectContext and getManagedObjectContext call. Upon being about to segue I check to make sure the destinationController will "respond to" this method, if so the data gets set.
clear?