Pass Managed Object Context from a ViewController to TarBarViewController using prepare for segue

Question

I am trying to pass the Core Data Managed Object Context from a ViewController (which is able to load the same from AppDelegate to a TabBarViewController.

AppDelegate.m

// Pass the managed object context to the root view controller (the login view)
LoginViewController *rootViewController = (LoginViewController *)self.window.rootViewController;
rootViewController.managedObjectContext = self.managedObjectContext;

LoginViewController.m

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if([segue.identifier isEqualToString:@"LoginSegue"]){
        UITabBarController *tabBarViewController = (UITabBarController *) [segue destinationViewController];
        ReceiptsListViewController *receiptsListViewController = (ReceiptsListViewController *) [[tabBarViewController viewControllers] objectAtIndex:5];
        receiptsListViewController.managedObjectContext = self.managedObjectContext;
    }
}

When i run it i encounter this error

2012-03-09 01:47:03.723 Peets[22893:fb03] -[UINavigationController setManagedObjectContext:]: unrecognized selector sent to instance 0x6d91900
2012-03-09 01:47:03.747 Peets[22893:fb03] *** WebKit discarded an uncaught exception in the webView:shouldInsertText:replacingDOMRange:givenAction: delegate: <NSInvalidArgumentException> -[UINavigationController setManagedObjectContext:]: unrecognized selector sent to instance 0x6d91900

rockstarberlin rockstarberlin · Accepted Answer · 2012-11-05T17:21:04

I don't understand exactly how you want to pass the MOC from a VC to a TBVC. Usually the RootViewController is the TBVC. If this is your case too you pass the MOC like this:

#import "AppDelegate.h"
#import "MasterViewController.h"

@implementation AppDelegate

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    UITabBarController *tabController = (UITabBarController *)self.window.rootViewController;

    UINavigationController *navigationController = (UINavigationController *)[[tabController viewControllers] objectAtIndex:0];
    MasterViewController *controller = (MasterViewController *)[[navigationController viewControllers] objectAtIndex:0];
    controller.managedObjectContext = self.managedObjectContext;

    navigationController = (UINavigationController *)[[tabController viewControllers] objectAtIndex:1];
    controller = (MasterViewController *)[[navigationController viewControllers] objectAtIndex:0];
    controller.managedObjectContext = self.managedObjectContext;

    navigationController = (UINavigationController *)[[tabController viewControllers] objectAtIndex:2];
    controller = (MasterViewController *)[[navigationController viewControllers] objectAtIndex:0];
    controller.managedObjectContext = self.managedObjectContext;

    return YES;
}

BTW: This example is based on the Master-Detail Application templante in Xcode. By default it has no TBVC, but if you add an TBVC like in the screenshot the code above will work.

enter image description here

Pass Managed Object Context from a ViewController to TarBarViewController using prepare for segue

2 Answers