My app doesn't show anything in the iOS simulator

Question

I am learning about how this article program description At the end of the page of Table View Controller you have to run you're app to see if everything works but i don't see anything in the iOS simulator besides that everything is black and at the top carrier and time.

One time i'm getting the error Locations[1203:fb03] Applications are expected to have a root view controller at the end of application launch And another time

App delegate header file:

#import <UIKit/UIKit.h>

UINavigationController *navigationController;

@interface LocationsAppDelegate : UIResponder <UIApplicationDelegate>

@property (nonatomic, retain) UINavigationController *navigationController;
@property (strong, nonatomic) UIWindow *window;
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator        *persistentStoreCoordinator;

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;



@end

App delegate Implementation file:

#import "LocationsAppDelegate.h"
#import "RootViewController.h"


@implementation LocationsAppDelegate;
@synthesize navigationController;

@synthesize window = _window;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize managedObjectModel = __managedObjectModel;
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:    (NSDictionary *)launchOptions {

RootViewController *rootViewController = [[RootViewController alloc]
                                          initWithStyle:UITableViewStylePlain];

NSManagedObjectContext *context = [self managedObjectContext];
if (!context) {
    // Handle the error.
}
// Pass the managed object context to the view controller.
rootViewController.managedObjectContext = context;

UINavigationController *aNavigationController = [[UINavigationController alloc]
                                                     initWithRootViewController:rootViewController];
self.navigationController = aNavigationController;

[_window addSubview:[navigationController view]];
[_window makeKeyAndVisible];


[rootViewController release];
[aNavigationController release];

return YES;
}


- (void)applicationWillTerminate:(UIApplication *)application
{
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
}

- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil)
{
    if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error])
    {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
        } 
    }
}

#pragma mark - Core Data stack

/**
 Returns the managed object context for the application.
 If the context doesn't already exist, it is created and bound to the persistent store    coordinator for the application.
 */
- (NSManagedObjectContext *)managedObjectContext
{
if (__managedObjectContext != nil)
{
    return __managedObjectContext;
}

NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
    __managedObjectContext = [[NSManagedObjectContext alloc] init];
    [__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;
}

/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created from the application's model.
 */
- (NSManagedObjectModel *)managedObjectModel
{
if (__managedObjectModel != nil)
{
    return __managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Locations"     withExtension:@"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return __managedObjectModel;
}

/**
 Returns the persistent store coordinator for the application.
 If the coordinator doesn't already exist, it is created and the application's store added     to it.
 */
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil)
{
    return __persistentStoreCoordinator;
}

NSURL *storeURL = [[self applicationDocumentsDirectory]    URLByAppendingPathComponent:@"Locations.sqlite"];

NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]   initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
{
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}    

return __persistentStoreCoordinator;
}

#pragma mark - Application's Documents directory

/**
Returns the URL to the application's Documents directory.
 */
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory   inDomains:NSUserDomainMask] lastObject];
}

@end

View controller header file:

#import <CoreLocation/CoreLocation.h>

@interface RootViewController : UITableViewController <CLLocationManagerDelegate> {

NSMutableArray *eventsArray;
NSManagedObjectContext *managedObjectContext;

CLLocationManager *locationManager;
UIBarButtonItem *addButton;
}

@property (nonatomic, retain) NSMutableArray *eventsArray;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;

@property (nonatomic, retain) CLLocationManager *locationManager;
@property (nonatomic, retain) UIBarButtonItem *addButton;


@end

View controller implementation file

//
//  RootViewController.m
//  Locations


#import "RootViewController.h"

@implementation RootViewController

@synthesize eventsArray;
@synthesize managedObjectContext;
@synthesize addButton;
@synthesize locationManager;

- (CLLocationManager *)locationManager {

if (locationManager != nil) {
    return locationManager;
}

locationManager = [[CLLocationManager alloc] init];
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
locationManager.delegate = self;

return locationManager;
}

- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
       fromLocation:(CLLocation *)oldLocation {
addButton.enabled = YES;
}

- (void)locationManager:(CLLocationManager *)manager
   didFailWithError:(NSError *)error {
addButton.enabled = NO;
}

#pragma mark - View lifecycle

- (void)viewDidLoad {


[super viewDidLoad];
// Set the title.
self.title = @"Locations";

// Set up the buttons.
self.navigationItem.leftBarButtonItem = self.editButtonItem;

addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd
                                                          target:self     action:@selector(addEvent)];
addButton.enabled = NO;
self.navigationItem.rightBarButtonItem = addButton;

// Start the location manager.
[[self locationManager] startUpdatingLocation];
}

- (void)viewDidUnload {
self.eventsArray = nil;
self.locationManager = nil;
self.addButton = nil;
}


- (void)dealloc {
[managedObjectContext release];
[eventsArray release];
[locationManager release];
[addButton release];
[super dealloc];
}



#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
#warning Potentially incomplete method implementation.
// Return the number of sections.
return 0;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
#warning Incomplete method implementation.
// Return the number of rows in the section.
return 0;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath   *)indexPath
{
static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault   reuseIdentifier:CellIdentifier];
}

// Configure the cell...

return cell;
}

   #pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath  *)indexPath
{
// Navigation logic may go here. Create and push another view controller.
/*
 <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc]  initWithNibName:@"<#Nib name#>" bundle:nil];
 // ...
 // Pass the selected object to the new view controller.
 [self.navigationController pushViewController:detailViewController animated:YES];
 */
}

 @end

Can someone please help me out??

Answer 1

I feel like Captain Obvious, but you forgot to set window.rootViewController.