Embed a MasterDetail template inside of a tabbar - ios7

Question

Okay, so I'm trying to embed my entire applications already created using the MasterDetail template inside of a tab controller.
I get an error because the app delegate places the context on the top view controller or something like that and i'm not sure where to redirect it to.
Now, I have searched it and found this: iOS MasterDetail app inside TabController - where to start?
but this isn't particularly helpful because the solution just gives more errors.
UINavigationController *navigationController = (UINavigationController *)self.window.rootViewController;
MasterViewController *controller = (MasterViewController *)navigationController.topViewController;
controller.managedObjectContext = self.managedObjectContext;
Errorlog:
2013-11-07 07:47:01.217 RoslynCAD[4491:70b] -[UITabBarController topViewController]: unrecognized selector sent to instance 0x9d72fe0
2013-11-07 07:47:01.220 RoslynCAD[4491:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITabBarController topViewController]: unrecognized selector sent to instance 0x9d72fe0'
*** First throw call stack:
(
0 CoreFoundation 0x01cf75e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x01a7a8b6 objc_exception_throw + 44
2 CoreFoundation 0x01d94903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x01ce790b ___forwarding___ + 1019
4 CoreFoundation 0x01ce74ee _CF_forwarding_prep_0 + 14
5 RoslynCAD 0x0000b9f6 -[AppDelegate application:didFinishLaunchingWithOptions:] + 278
6 UIKit 0x007e2355 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 309
7 UIKit 0x007e2b95 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1536
8 UIKit 0x007e73a8 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
9 UIKit 0x007fb87c -[UIApplication handleEvent:withNewEvent:] + 3447
10 UIKit 0x007fbde9 -[UIApplication sendEvent:] + 85
11 UIKit 0x007e9025 _UIApplicationHandleEvent + 736
12 GraphicsServices 0x0262e2f6 _PurpleEventCallback + 776
13 GraphicsServices 0x0262de01 PurpleEventCallback + 46
14 CoreFoundation 0x01c72d65 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
15 CoreFoundation 0x01c72a9b __CFRunLoopDoSource1 + 523
16 CoreFoundation 0x01c9d77c __CFRunLoopRun + 2156
17 CoreFoundation 0x01c9cac3 CFRunLoopRunSpecific + 467
18 CoreFoundation 0x01c9c8db CFRunLoopRunInMode + 123
19 UIKit 0x007e6add -[UIApplication _run] + 840
20 UIKit 0x007e8d3b UIApplicationMain + 1225
21 RoslynCAD 0x000147ed main + 141
22 libdyld.dylib 0x0308370d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
and
int main(int argc, char * argv[])
{
#autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}
UPDATE:
I have edited my code:
UITabBarController *tabController = (UITabBarController *)self.window.rootViewController;
MasterViewController *controller = (MasterViewController *)[tabController.viewControllers objectAtIndex:0];
controller.managedObjectContext = self.managedObjectContext;
And I get this error now
2013-11-10 00:37:03.455 RoslynCAD[6783:70b] -[UINavigationController setManagedObjectContext:]: unrecognized selector sent to instance 0x9e54c40
(lldb)

Answer 1

The error is clear. You are doing this:
UINavigationController *navigationController = (UINavigationController *)self.window.rootViewController;
MasterViewController *controller = (MasterViewController *)navigationController.topViewController;
The error comes from the second line. The error is telling you that navigationController is actually a UITabBarController, not a UINavigationController.
You want:
UITabBarController *tabController = (UITabBarController *)self.window.rootViewController;
// Get what you need from the tab controller