Navigation View Controller question

ContactsTableViewController.h

#import <UIKit/UIKit.h>
#import "CoreDataTableViewController.h"

@interface ContactsTableViewController : UITableViewController<UINavigationControllerDelegate> {
    UINavigationController *navController;
}

@property (nonatomic, strong) NSArray *contacts;

@end

ContactsTableViewController.m

#import "ContactsTableViewController.h"
#import "AddressBookAppDelegate.h"
#import "ContactDetailViewController.h"
#import "Contact.h"

@implementation ContactsTableViewController

@synthesize contacts = _contacts;

- (void)fetchData
{
    AddressBookAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    
    NSManagedObjectContext *context = [appDelegate managedObjectContext];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Contact" 
                                              inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    request.entity = entity;
    
    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
    request.sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
    
    NSError *error = nil;
    self.contacts = [context executeFetchRequest:request error:&error];
    if(error == nil){
        [self.tableView reloadData];
    }
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    self.navigationController.delegate = self;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Table view data source

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"Show Contact"]) {
        Contact *contact = [self.contacts objectAtIndex:[self.tableView.indexPathForSelectedRow row]];
        [segue.destinationViewController setContact:contact];
    }
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.contacts count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Contact Cell";
    
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }
    
    // Configure the cell...
    Contact *contact = [self.contacts objectAtIndex:[indexPath row]];
    cell.textLabel.text = contact.name;
    
    return cell;
}

- (void)navigationController:(UINavigationController *)navigationController 
      willShowViewController:(UIViewController *)viewController 
                    animated:(BOOL)animated 
{
    [self fetchData];
}

@end