ios新手..故事板实现表视图的修改以及删除的问题


#import "ViewController.h"@interface ViewController ()
@property (strong, nonatomic) IBOutlet UITextField *textfield;@end@implementation ViewController- (void)viewDidLoad {
    [super viewDidLoad];
    self.navigationItem.rightBarButtonItem=self.editButtonItem;
    self.navigationItem.title=@"xiugai";
    self.textfield.hidden=YES;
    _muary=[NSMutableArray arrayWithObjects:@"yiwu",@"hangzou",@"anji", nil];
    // Do any additional setup after loading the view, typically from a nib.
}- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}- (BOOL)textFieldShouldReturn:(UITextField *)textField{
    [textField resignFirstResponder];
    return YES;
}- (void)setEditing:(BOOL)editing animated:(BOOL)animated{
    [super setEditing:editing animated:animated];
    [self.tableView setEditing:editing animated:YES];
    if (editing) {
        self.textfield.hidden=NO;
    }else{
        self.textfield.hidden=YES;
    }
}- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    return ([_muary count]+1);
}.........
大致上照着书上打的，而且故事板里面也有navigationitem,在表格单元格的上面。但是编译出来navigationitem就不见了 
还有这个表视图是navigationcontroller里面自带的根视图。求大神解答